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Sample records for chromosome segregation

  1. Chromosome segregation in plant meiosis

    Directory of Open Access Journals (Sweden)

    Linda eZamariola

    2014-06-01

    Full Text Available Faithful chromosome segregation in meiosis is essential for ploidy stability over sexual life cycles. In plants, defective chromosome segregation caused by gene mutations or other factors leads to the formation of unbalanced or unreduced gametes creating aneuploid or polyploid progeny, respectively. Accurate segregation requires the coordinated execution of conserved processes occurring throughout the two meiotic cell divisions. Synapsis and recombination ensure the establishment of chiasmata that hold homologous chromosomes together allowing their correct segregation in the first meiotic division, which is also tightly regulated by cell-cycle dependent release of cohesin and monopolar attachment of sister kinetochores to microtubules. In meiosis II, bi-orientation of sister kinetochores and proper spindle orientation correctly segregate chromosomes in four haploid cells. Checkpoint mechanisms acting at kinetochores control the accuracy of kinetochore-microtubule attachment, thus ensuring the completion of segregation. Here we review the current knowledge on the processes taking place during chromosome segregation in plant meiosis, focusing on the characterization of the molecular factors involved.

  2. Bacterial chromosome organization and segregation.

    Science.gov (United States)

    Badrinarayanan, Anjana; Le, Tung B K; Laub, Michael T

    2015-01-01

    If fully stretched out, a typical bacterial chromosome would be nearly 1 mm long, approximately 1,000 times the length of a cell. Not only must cells massively compact their genetic material, but they must also organize their DNA in a manner that is compatible with a range of cellular processes, including DNA replication, DNA repair, homologous recombination, and horizontal gene transfer. Recent work, driven in part by technological advances, has begun to reveal the general principles of chromosome organization in bacteria. Here, drawing on studies of many different organisms, we review the emerging picture of how bacterial chromosomes are structured at multiple length scales, highlighting the functions of various DNA-binding proteins and the impact of physical forces. Additionally, we discuss the spatial dynamics of chromosomes, particularly during their segregation to daughter cells. Although there has been tremendous progress, we also highlight gaps that remain in understanding chromosome organization and segregation. PMID:26566111

  3. A sexy spin on nonrandom chromosome segregation.

    Science.gov (United States)

    Charville, Gregory W; Rando, Thomas A

    2013-06-01

    Nonrandom chromosome segregation is an intriguing phenomenon linked to certain asymmetric stem cell divisions. In a recent report in Nature, Yadlapalli and Yamashita (2013) observe nonrandom segregation of X and Y chromosomes in Drosophila germline stem cells and shed light on the complex mechanisms of this fascinating process. PMID:23746972

  4. Progressive segregation of the Escherichia coli chromosome

    DEFF Research Database (Denmark)

    Nielsen, Henrik Jørck; Youngren, Brenda; Hansen, Flemming G.;

    2006-01-01

    We have followed the fate of 14 different loci around the Escherichia coli chromosome in living cells at slow growth rate using a highly efficient labelling system and automated measurements. Loci are segregated as they are replicated, but with a marked delay. Most markers segregate in a smooth...

  5. Dynamics of chromosome segregation in Escherichia coli

    DEFF Research Database (Denmark)

    Nielsen, Henrik Jørck

    2007-01-01

    Since the 1960’es the conformation and segregation of the chromosome in Escherichia coli has been a subject of interest for many scientists. However, after 40 years of research, we still know incredibly little about how the chromosome is organized inside the cell, how it manages to duplicate...... method enabled us to start the analysis on the distribution of various chromosomal loci inside slowly growing cells. With the actual counting and measuring no longer being any problem we could easily analyze 14 loci distributed on the E.coli chromosome. More than 15.000 cells were analyzed in total...... the new system, which is based on the pMT1 par system from Yersenia pestis, we labeled loci on opposite sides of the E.coli chromosome simultaneously and were able to show that the E.coli chromosome is organized with one chromosomal arm in each cell half. This astounding result is described in Paper III...

  6. Plasmid and chromosome segregation in prokaryotes

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    Møller-Jensen, Jakob; Bugge Jensen, Rasmus; Gerdes, Kenn

    2000-01-01

    Recent major advances in the understanding of prokaryotic DNA segregation have been achieved by using fluorescence microscopy to visualize the localization of cellular components. Plasmids and bacterial chromosomes are partitioned in a highly dynamic fashion, suggesting the presence of a mitotic......-like apparatus in prokaryotes. The identification of chromosomal homologues of the well-characterized plasmid partitioning genes indicates that there could be a general mechanism of bacterial DNA partitioning. Udgivelsesdato: July 1...

  7. PICH promotes mitotic chromosome segregation

    DEFF Research Database (Denmark)

    Nielsen, Christian Thomas Friberg; Hickson, Ian D

    2016-01-01

    PICH is an SNF2-family DNA translocase that appears to play a role specifically in mitosis. Characterization of PICH in human cells led to the initial discovery of "ultra-fine DNA bridges" (UFBs) that connect the 2 segregating DNA masses in the anaphase of mitosis. These bridge structures, which...... arise from specific regions of the genome, are a normal feature of anaphase but had escaped detection previously because they do not stain with commonly used DNA dyes. Nevertheless, UFBs are important for genome maintenance because defects in UFB resolution can lead to cytokinesis failure. We reported...... recently that PICH stimulates the unlinking (decatenation) of entangled DNA by Topoisomerase IIα (Topo IIα), and is important for the resolution of UFBs. We also demonstrated that PICH and Topo IIα co-localize at the rDNA (rDNA). In this Extra View article, we discuss the mitotic roles of PICH and explore...

  8. Dynamics of Escherichia coli chromosome segregation during multifork replication.

    Science.gov (United States)

    Nielsen, Henrik J; Youngren, Brenda; Hansen, Flemming G; Austin, Stuart

    2007-12-01

    Slowly growing Escherichia coli cells have a simple cell cycle, with replication and progressive segregation of the chromosome completed before cell division. In rapidly growing cells, initiation of replication occurs before the previous replication rounds are complete. At cell division, the chromosomes contain multiple replication forks and must be segregated while this complex pattern of replication is still ongoing. Here, we show that replication and segregation continue in step, starting at the origin and progressing to the replication terminus. Thus, early-replicated markers on the multiple-branched chromosomes continue to separate soon after replication to form separate protonucleoids, even though they are not segregated into different daughter cells until later generations. The segregation pattern follows the pattern of chromosome replication and does not follow the cell division cycle. No extensive cohesion of sister DNA regions was seen at any growth rate. We conclude that segregation is driven by the progression of the replication forks.

  9. Dynamics of Escherichia coli Chromosome Segregation during Multifork Replication▿

    Science.gov (United States)

    Nielsen, Henrik J.; Youngren, Brenda; Hansen, Flemming G.; Austin, Stuart

    2007-01-01

    Slowly growing Escherichia coli cells have a simple cell cycle, with replication and progressive segregation of the chromosome completed before cell division. In rapidly growing cells, initiation of replication occurs before the previous replication rounds are complete. At cell division, the chromosomes contain multiple replication forks and must be segregated while this complex pattern of replication is still ongoing. Here, we show that replication and segregation continue in step, starting at the origin and progressing to the replication terminus. Thus, early-replicated markers on the multiple-branched chromosomes continue to separate soon after replication to form separate protonucleoids, even though they are not segregated into different daughter cells until later generations. The segregation pattern follows the pattern of chromosome replication and does not follow the cell division cycle. No extensive cohesion of sister DNA regions was seen at any growth rate. We conclude that segregation is driven by the progression of the replication forks. PMID:17905986

  10. CHROMOSOME SEGREGATION: NOVEL INSIGHTS INTO THE MECHANISM AND REGULATION

    Directory of Open Access Journals (Sweden)

    Miroslava Pozgajova

    2013-02-01

    Full Text Available A crucial feature of every healthy living organism is accurate segregation of chromosomes. Errors in this process may lead to aneuploidy, which is responsible for diverse genetic defects and diseases such as Down syndrome, miscarriages, cancer and others. Although, chromosome segregation has been studied intensively in the past, the exact mechanism of accurate chromosome segregation still remains unclear. Identification and characterization of proteins and protein complexes involved in this process is essential for understanding of processes that lead to chromosome missegregation. Basic molecular mechanism share common principles in animals, humans, plants and unicellular organisms; it is therefore possible to study these mechanisms in simple model organisms such as yeasts. The fission yeast Schizosaccharomyces pombe is an excellent model organism to study the function and regulation of chromosome segregation in both mitosis and meiosis.

  11. Dynamics of Escherichia coli Chromosome Segregation during Multifork Replication

    DEFF Research Database (Denmark)

    Nielsen, Henrik Jørck; Youngren, Brenda; Hansen, Flemming G.;

    2007-01-01

    Slowly growing Escherichia coli cells have a simple cell cycle, with replication and progressive segregation of the chromosome completed before cell division. In rapidly growing cells, initiation of replication occurs before the previous replication rounds are complete. At cell division...

  12. A polarity factor takes the lead in chromosome segregation

    OpenAIRE

    Kirkpatrick, Clare; Viollier, Patrick

    2010-01-01

    Several recent studies shed light on how bacteria achieve rapid and accurate chromosome segregation through an interplay of Par-type partitioning systems, cytokinesis regulators and a polarity determinant.

  13. Chromosome segregation errors: a double-edged sword

    NARCIS (Netherlands)

    Janssen, A.

    2012-01-01

    Unequal separation of the mother cells’ DNA over its two daughter cells upon cell division is a prevalent phenotype found in cancer cells. This imbalanced nuclear division manifests itself as chromosome segregation errors in the final phases of Mitosis. Chromosome unstable (CIN) cancer cells continu

  14. Disruption of human vigilin impairs chromosome condensation and segregation.

    Science.gov (United States)

    Wei, Ling; Xie, Xiaoyan; Li, Junhong; Li, Ran; Shen, Wenyan; Duan, Shuwang; Zhao, Rongce; Yang, Wenli; Liu, Qiuying; Fu, Qiang; Qin, Yang

    2015-11-01

    Appropriate packaging and condensation are critical for eukaryotic chromatin's accommodation and separation during cell division. Human vigilin, a multi-KH-domain nucleic acid-binding protein, is associated with alpha satellites of centromeres. DDP1, a vigilin's homolog, is implicated with chromatin condensation and segregation. The expression of vigilin was previously reported to elevate in highly proliferating tissues and increased in a subset of hepatocellular carcinoma patients. Other studies showed that vigilin interacts with CTCF, contributes to regulation of imprinted genes Igf2/H19, and colocalizes with HP1α on heterochromatic satellite 2 and β-satellite repeats. These studies indicate that human vigilin might be involved in chromatin remodeling and regular cell growth. To investigate the potential role of human vigilin in cell cycle, the correlations between vigilin and chromosomal condensation and segregation were studied. Depletion of human vigilin by RNA interference in HepG2 cells resulted in chromosome undercondensation and various chromosomal defects during mitotic phase, including chromosome misalignments, lagging chromosomes, and chromosome bridges. Aberrant polyploid nucleus in telophase was also observed. Unlike the abnormal staining pattern of chromosomes, the shape of spindle was normal. Furthermore, the chromatin showed a greater sensitivity to MNase digestion. Collectively, our findings show that human vigilin apparently participates in chromatin condensation and segregation. PMID:26032007

  15. Abnormal Chromosome Segregation May Trigger Tumors

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ Cancer is a primary threat to human health as it kills millions of people each year.Scientists have shown that 75% of human cancers have an abnormal number of chromosomes in cells,and the proportion of the cells with an abnormal chromosome number is tightly and positively related to malignance progression and metastasis of cancers. But the pathological mechanism behind the anomaly still remains unknown.

  16. A novel chromosome segregation mechanism during female meiosis.

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    McNally, Karen Perry; Panzica, Michelle T; Kim, Taekyung; Cortes, Daniel B; McNally, Francis J

    2016-08-15

    In a wide range of eukaryotes, chromosome segregation occurs through anaphase A, in which chromosomes move toward stationary spindle poles, anaphase B, in which chromosomes move at the same velocity as outwardly moving spindle poles, or both. In contrast, Caenorhabditis elegans female meiotic spindles initially shorten in the pole-to-pole axis such that spindle poles contact the outer kinetochore before the start of anaphase chromosome separation. Once the spindle pole-to-kinetochore contact has been made, the homologues of a 4-μm-long bivalent begin to separate. The spindle shortens an additional 0.5 μm until the chromosomes are embedded in the spindle poles. Chromosomes then separate at the same velocity as the spindle poles in an anaphase B-like movement. We conclude that the majority of meiotic chromosome movement is caused by shortening of the spindle to bring poles in contact with the chromosomes, followed by separation of chromosome-bound poles by outward sliding. PMID:27335123

  17. Time scale of entropic segregation of flexible polymers in confinement: Implications for chromosome segregation in filamentous bacteria

    OpenAIRE

    Arnold, Axel; Jun, Suckjoon

    2007-01-01

    We report molecular dynamics simulations of the segregation of two overlapping chains in cylindrical confinement. We find that the entropic repulsion between the chains can be sufficiently strong to cause segregation on a time scale that is short compared to the one for diffusion. This result implies that entropic driving forces are sufficiently strong to cause rapid bacterial chromosome segregation.

  18. csi2p modulates microtubule dynamics and organizes the bipolar spindle for chromosome segregation

    OpenAIRE

    Costa, Judite; Fu, Chuanhai; Khare, V. Mohini; Tran, Phong T.

    2014-01-01

    Proper chromosome segregation is of paramount importance for proper genetic inheritance. Defects in chromosome segregation can lead to aneuploidy, which is a hallmark of cancer cells. Eukaryotic chromosome segregation is accomplished by the bipolar spindle. Additional mechanisms, such as the spindle assembly checkpoint and centromere positioning, further help to ensure complete segregation fidelity. Here we present the fission yeast csi2 +. csi2p localizes to the spindle poles, where it regul...

  19. Proposed Physical Mechanism of Chromosome Segregation in Caulobacter crescentus

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    Banigan, Edward; Gelbart, Michael; Gitai, Zemer; Liu, Andrea; Wingreen, Ned

    2010-03-01

    Chromosome segregation is a fundamental process for all cells, but the force-generating mechanisms that drive chromosome movements in bacteria are especially unclear. In Caulobacter crescentus, recent work has demonstrated that a structure made up of the ParA protein elongates from one cell pole and interacts with ParB, a protein binding to the chromosome near the origin of replication (ori). ParB disassembles ParA, causing ParA to pull ParB, and thus, the ori to the opposite end of the cell. We performed Brownian dynamics simulations of this system in order to uncover the physical mechanism of this motion. We find that motion of the ori is robust to several variations of the model as long as a steady-state concentration gradient of ParA is established in the moving frame of the ParB-decorated chromosome. We suggest that the mechanism is ``self-diffusiophoretic'': by disassembling ParA, ParB creates a concentration gradient of ParA so that the ParA concentration is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the gradient in the desired direction.

  20. Physical Model of Segregation of E.coli Chromosomes using Molecular Dynamics

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    Alnahhas, Faisal; Kharel, Savan

    2016-03-01

    Chromosome segregation is one of the most interesting physical processes during a bacterial cell cycle. We will use molecular dynamics simulations which will help us understand how strongly confined polymer segregates. In the presentation, we will discuss how segregation of initially overlapping circular chromosome occurs during a cell cycle. In particular, we will describe the role played by entropic mechanism in the demixing of overlapping circular polymer confined in a cylindrical boundary. We discuss how our polymer chains modeled as an E-coli chromosome experiences an effective repulsion, which ultimately leads to partition driven by the entropic forces. Also, we will also discuss how the segregation of circular chromosome in cylindrical confinement differs from a spherical confinement. Finally, we will discuss the role played by proteins and supercoiling in during the segregation process.

  1. Dysfunctional MreB inhibits chromosome segregation in Escherichia coli

    DEFF Research Database (Denmark)

    Kruse, Thomas; Møller-Jensen, Jakob; Løbner-Olesen, Anders;

    2003-01-01

    The mechanism of prokaryotic chromosome segregation is not known. MreB, an actin homolog, is a shape-determining factor in rod-shaped prokaryotic cells. Using immunofluorescence microscopy we found that MreB of Escherichia coli formed helical filaments located beneath the cell surface. Flow...... cytometric and cytological analyses indicated that MreB-depleted cells segregated their chromosomes in pairs, consistent with chromosome cohesion. Overexpression of wild-type MreB inhibited cell division but did not perturb chromosome segregation. Overexpression of mutant forms of MreB inhibited cell...... division, caused abnormal MreB filament morphology and induced severe localization defects of the nucleoid and of the oriC and terC chromosomal regions. The chromosomal terminus regions appeared cohered in both MreB-depleted cells and in cells overexpressing mutant forms of MreB. Our observations indicate...

  2. DNA damage response during mitosis induces whole chromosome mis-segregation

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    Bakhoum, Samuel F.; Kabeche, Lilian; Murnane, John P.; Zaki, Bassem I.; Compton, Duane A.

    2014-01-01

    Many cancers display both structural (s-CIN) and numerical (w-CIN) chromosomal instabilities. Defective chromosome segregation during mitosis has been shown to cause DNA damage that induces structural rearrangements of chromosomes (s-CIN). In contrast, whether DNA damage can disrupt mitotic processes to generate whole chromosomal instability (w-CIN) is unknown. Here we show that activation of the DNA damage response (DDR) during mitosis selectively stabilizes kinetochore-microtubule (k-MT) attachments to chromosomes through Aurora-A and Plk1 kinases, thereby increasing the frequency of lagging chromosomes during anaphase. Inhibition of DDR proteins, ATM or Chk2, abolishes the effect of DNA damage on k-MTs and chromosome segregation, whereas activation of the DDR in the absence of DNA damage is sufficient to induce chromosome segregation errors. Finally, inhibiting the DDR during mitosis in cancer cells with persistent DNA damage suppresses inherent chromosome segregation defects. Thus, DDR during mitosis inappropriately stabilizes k-MTs creating a link between s-CIN and w-CIN. PMID:25107667

  3. The dynamics of signal amplification by macromolecular assemblies for the control of chromosome segregation

    Directory of Open Access Journals (Sweden)

    Semin eLee

    2014-09-01

    Full Text Available The control of chromosome segregation relies on the spindle assembly checkpoint (SAC, a complex regulatory system that ensures the high fidelity of chromosome segregation in higher organisms by delaying the onset of anaphase until each chromosome is properly bi-oriented on the mitotic spindle. Central to this process is the establishment of multiple yet specific protein-protein interactions in a narrow time-space window. Here we discuss the highly dynamic nature of multi-protein complexes that control chromosome segregation in which an intricate network of weak but cooperative interactions modulate signal amplification to ensure a proper SAC response. We also discuss the current structural understanding of the communication between the SAC and the kinetochore; how transient interactions can regulate the assembly and disassembly of the SAC as well as the challenges and opportunities for the definition and the manipulation of the flow of information in SAC signaling.

  4. How chromosome mis-segregation leads to cancer: lessons from BubR1 mouse models.

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    Lee, Hyunsook

    2014-10-31

    Alteration in chromosome numbers and structures instigate and foster massive genetic instability. As Boveri has seen a hundred years ago (Boveri, 1914; 2008), aneuploidy is hallmark of many cancers. However, whether aneuploidy is the cause or the result of cancer is still at debate. The molecular mechanism behind aneuploidy includes the chromo-some mis-segregation in mitosis by the compromise of spindle assembly checkpoint (SAC). SAC is an elaborate network of proteins, which monitor that all chromosomes are bipolarly attached with the spindles. Therefore, the weakening of the SAC is the major reason for chromosome number instability, while complete compromise of SAC results in detrimental death, exemplified in natural abortion in embryonic stage. Here, I will review on the recent progress on the understanding of chromosome mis-segregation and cancer, based on the comparison of different mouse models of BubR1, the core component of SAC. PMID:25256220

  5. Chromosome mis-segregation and cytokinesis failure in trisomic human cells.

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    Nicholson, Joshua M; Macedo, Joana C; Mattingly, Aaron J; Wangsa, Darawalee; Camps, Jordi; Lima, Vera; Gomes, Ana M; Dória, Sofia; Ried, Thomas; Logarinho, Elsa; Cimini, Daniela

    2015-05-05

    Cancer cells display aneuploid karyotypes and typically mis-segregate chromosomes at high rates, a phenotype referred to as chromosomal instability (CIN). To test the effects of aneuploidy on chromosome segregation and other mitotic phenotypes we used the colorectal cancer cell line DLD1 (2n = 46) and two variants with trisomy 7 or 13 (DLD1+7 and DLD1+13), as well as euploid and trisomy 13 amniocytes (AF and AF+13). We found that trisomic cells displayed higher rates of chromosome mis-segregation compared to their euploid counterparts. Furthermore, cells with trisomy 13 displayed a distinctive cytokinesis failure phenotype. We showed that up-regulation of SPG20 expression, brought about by trisomy 13 in DLD1+13 and AF+13 cells, is sufficient for the cytokinesis failure phenotype. Overall, our study shows that aneuploidy can induce chromosome mis-segregation. Moreover, we identified a trisomy 13-specific mitotic phenotype that is driven by up-regulation of a gene encoded on the aneuploid chromosome.

  6. Role of the Number of Microtubules in Chromosome Segregation during Cell Division

    CERN Document Server

    Bertalan, Zsolt; La Porta, Caterina A M; Zapperi, Stefano

    2015-01-01

    Faithful segregation of genetic material during cell division requires alignment of chromosomes between two spindle poles and attachment of their kinetochores to each of the poles. Failure of these complex dynamical processes leads to chromosomal instability (CIN), a characteristic feature of several diseases including cancer. While a multitude of biological factors regulating chromosome congression and bi-orientation have been identified, it is still unclear how they are integrated so that coherent chromosome motion emerges from a large collection of random and deterministic processes. Here we address this issue by a three dimensional computational model of motor-driven chromosome congression and bi-orientation during mitosis. Our model reveals that successful cell division requires control of the total number of microtubules: if this number is too small bi-orientation fails, while if it is too large not all the chromosomes are able to congress. The optimal number of microtubules predicted by our model compa...

  7. SMC is recruited to oriC by ParB and promotes chromosome segregation in Streptococcus pneumoniae

    NARCIS (Netherlands)

    Minnen, Anita; Attaiech, Laetitia; Thon, Maria; Gruber, Stephan; Veening, Jan-Willem

    2011-01-01

    Segregation of replicated chromosomes is an essential process in all organisms. How bacteria, such as the oval-shaped human pathogen Streptococcus pneumoniae, efficiently segregate their chromosomes is poorly understood. Here we show that the pneumococcal homologue of the DNA-binding protein ParB re

  8. Repulsive forces between looping chromosomes induce entropy-driven segregation.

    Directory of Open Access Journals (Sweden)

    Manfred Bohn

    Full Text Available One striking feature of chromatin organization is that chromosomes are compartmentalized into distinct territories during interphase, the degree of intermingling being much smaller than expected for linear chains. A growing body of evidence indicates that the formation of loops plays a dominant role in transcriptional regulation as well as the entropic organization of interphase chromosomes. Using a recently proposed model, we quantitatively determine the entropic forces between chromosomes. This Dynamic Loop Model assumes that loops form solely on the basis of diffusional motion without invoking other long-range interactions. We find that introducing loops into the structure of chromatin results in a multi-fold higher repulsion between chromosomes compared to linear chains. Strong effects are observed for the tendency of a non-random alignment; the overlap volume between chromosomes decays fast with increasing loop number. Our results suggest that the formation of chromatin loops imposes both compartmentalization as well as order on the system without requiring additional energy-consuming processes.

  9. Looping in on Ndc80 - how does a protein loop at the kinetochore control chromosome segregation?

    DEFF Research Database (Denmark)

    Nilsson, Jakob

    2012-01-01

    Segregation of chromosomes during mitosis requires the interaction of dynamic microtubules with the kinetochore, a large protein structure established on the centromere region of sister chromatids. The core microtubule-binding activity of the kinetochore resides in the KMN network, an outer...

  10. Connecting the dots of the bacterial cell cycle: Coordinating chromosome replication and segregation with cell division.

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    Hajduk, Isabella V; Rodrigues, Christopher D A; Harry, Elizabeth J

    2016-05-01

    Proper division site selection is crucial for the survival of all organisms. What still eludes us is how bacteria position their division site with high precision, and in tight coordination with chromosome replication and segregation. Until recently, the general belief, at least in the model organisms Bacillus subtilis and Escherichia coli, was that spatial regulation of division comes about by the combined negative regulatory mechanisms of the Min system and nucleoid occlusion. However, as we review here, these two systems cannot be solely responsible for division site selection and we highlight additional regulatory mechanisms that are at play. In this review, we put forward evidence of how chromosome replication and segregation may have direct links with cell division in these bacteria and the benefit of recent advances in chromosome conformation capture techniques in providing important information about how these three processes mechanistically work together to achieve accurate generation of progenitor cells.

  11. The multiple roles of Bub1 in chromosome segregation during mitosis and meiosis

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    Marchetti, Francesco; Venkatachalam, Sundaresan

    2009-06-19

    Aneuploidy, any deviation from an exact multiple of the haploid number of chromosomes, is a common occurrence in cancer and represents the most frequent chromosomal disorder in newborns. Eukaryotes have evolved mechanisms to assure the fidelity of chromosome segregation during cell division that include a multiplicity of checks and controls. One of the main cell division control mechanisms is the spindle assembly checkpoint (SAC) that monitors the proper attachment of chromosomes to spindle fibers and prevents anaphase until all kinetochores are properly attached. The mammalian SAC is composed by at least 14 evolutionary-conserved proteins that work in a coordinated fashion to monitor the establishment of amphitelic attachment of all chromosomes before allowing cell division to occur. Among the SAC proteins, the budding uninhibited by benzimidazole protein 1 (Bub1), is a highly conserved protein of prominent importance for the proper functioning of the SAC. Studies have revealed many roles for Bub1 in both mitosis and meiosis, including the localization of other SAC proteins to the kinetochore, SAC signaling, metaphase congression and the protection of the sister chromatid cohesion. Recent data show striking sex specific differences in the response to alterations in Bub1 activity. Proper Bub1 functioning is particularly important during oogenesis in preventing the generation of aneuploid gametes that can have detrimental effects on the health status of the fetus and the newborn. These data suggest that Bub1 is a master regulator of SAC and chromosomal segregation in both mitosis and meiosis. Elucidating its many essential functions in regulating proper chromosome segregation can have important consequences for preventing tumorigenesis and developmental abnormalities.

  12. Tumor-specific chromosome mis-segregation controls cancer plasticity by maintaining tumor heterogeneity.

    Directory of Open Access Journals (Sweden)

    Yuanjie Hu

    Full Text Available Aneuploidy with chromosome instability is a cancer hallmark. We studied chromosome 7 (Chr7 copy number variation (CNV in gliomas and in primary cultures derived from them. We found tumor heterogeneity with cells having Chr7-CNV commonly occurs in gliomas, with a higher percentage of cells in high-grade gliomas carrying more than 2 copies of Chr7, as compared to low-grade gliomas. Interestingly, all Chr7-aneuploid cell types in the parental culture of established glioma cell lines reappeared in single-cell-derived subcultures. We then characterized the biology of three syngeneic glioma cultures dominated by different Chr7-aneuploid cell types. We found phenotypic divergence for cells following Chr7 mis-segregation, which benefited overall tumor growth in vitro and in vivo. Mathematical modeling suggested the involvement of chromosome instability and interactions among cell subpopulations in restoring the optimal equilibrium of tumor cell types. Both our experimental data and mathematical modeling demonstrated that the complexity of tumor heterogeneity could be enhanced by the existence of chromosomes with structural abnormality, in addition to their mis-segregations. Overall, our findings show, for the first time, the involvement of chromosome instability in maintaining tumor heterogeneity, which underlies the enhanced growth, persistence and treatment resistance of cancers.

  13. A minimal number of MELT repeats supports all functions of KNL1 in chromosome segregation

    DEFF Research Database (Denmark)

    Zhang, Gang; Lischetti, Tiziana; Nilsson, Jakob

    2013-01-01

    The Bub1-Bub3 and BubR1-Bub3 checkpoint complexes, or the Bubs, contribute to the accurate segregation of chromosomes during mitosis by promoting chromosome bi-orientation and halting exit from mitosis if this fails. The complexes associate with kinetochores during mitosis, which is required for ...... the number of MELT repeats to less than four reduced KNL1 functionality. Furthermore, we show that Protein Phosphatase 1 (PP1) binding to KNL1 in prometaphase reduces the levels of Bub proteins at kinetochores to approximately the level recruited by four active MELT repeats....

  14. A role for the fission yeast Rqh1 helicase in chromosome segregation

    DEFF Research Database (Denmark)

    Win, Thein Z; Mankouri, Hocine W; Hickson, Ian D;

    2005-01-01

    progression, and show lagging chromosomal DNA, which is particularly apparent in the rDNA locus. This mitotic delay is dependent on the spindle checkpoint, as deletion of mad2 abolishes the delay as well as the accumulation of Cut2 in rqh1delta cells. Furthermore, relieving replication fork arrest in the r...... replication forks or DNA breaks, but the precise mechanisms that lead to the development of cancer in these diseases have remained obscure. Here, we reveal a function for Rqh1 in chromosome segregation even in the absence of exogenous insult to the DNA. We show that cells lacking Rqh1 are delayed in anaphase...

  15. Interplay between type 1A topoisomerases and gyrase in chromosome segregation in Escherichia coli.

    Science.gov (United States)

    Usongo, Valentine; Tanguay, Cynthia; Nolent, Flora; Bessong, Jill Egbe; Drolet, Marc

    2013-04-01

    Escherichia coli possesses two type 1A topoisomerases, Topo I (topA) and Topo III (topB). Topo I relaxes excess negative supercoiling, and topA mutants can grow only in the presence of compensatory mechanisms, such as gyrase mutations. topB mutants grow as well as wild-type cells. In vitro, Topo III, but not Topo I, can efficiently decatenate DNA during replication. However, in vivo, a chromosome segregation defect is seen only when both type 1A topoisomerases are absent. Here we present experimental evidence for an interplay between gyrase and type 1A topoisomerases in chromosome segregation. We found that both the growth defect and the Par(-) phenotypes of a gyrB(Ts) mutant at nonpermissive temperatures were significantly corrected by deleting topA, but only when topB was present. Overproducing Topo IV, the major cellular decatenase, could not substitute for topB. We also show that overproducing Topo III at a very high level could suppress the Par(-) phenotype. We previously found that the growth and chromosome segregation defects of a triple topA rnhA gyrB(Ts) mutant in which gyrase supercoiling activity was strongly inhibited could be corrected by overproducing Topo III (V. Usongo, F. Nolent, P. Sanscartier, C. Tanguay, S. Broccoli, I. Baaklini, K. Drlica, and M. Drolet, Mol. Microbiol. 69:968-981, 2008). We show here that this overproduction could be bypassed by substituting the gyrB(Ts) allele for a gyrB(+) one or by growing cells in a minimal medium, conditions that reduced both topA- and rnhA-dependent unregulated replication. Altogether, our data point to a role for Topo III in chromosome segregation when gyrase is inefficient and suggest that Topo I plays an indirect role via supercoiling regulation. PMID:23396913

  16. Identification of Conserved MEL-28/ELYS Domains with Essential Roles in Nuclear Assembly and Chromosome Segregation.

    Directory of Open Access Journals (Sweden)

    Georgina Gómez-Saldivar

    2016-06-01

    Full Text Available Nucleoporins are the constituents of nuclear pore complexes (NPCs and are essential regulators of nucleocytoplasmic transport, gene expression and genome stability. The nucleoporin MEL-28/ELYS plays a critical role in post-mitotic NPC reassembly through recruitment of the NUP107-160 subcomplex, and is required for correct segregation of mitotic chromosomes. Here we present a systematic functional and structural analysis of MEL-28 in C. elegans early development and human ELYS in cultured cells. We have identified functional domains responsible for nuclear envelope and kinetochore localization, chromatin binding, mitotic spindle matrix association and chromosome segregation. Surprisingly, we found that perturbations to MEL-28's conserved AT-hook domain do not affect MEL-28 localization although they disrupt MEL-28 function and delay cell cycle progression in a DNA damage checkpoint-dependent manner. Our analyses also uncover a novel meiotic role of MEL-28. Together, these results show that MEL-28 has conserved structural domains that are essential for its fundamental roles in NPC assembly and chromosome segregation.

  17. Sex ratio in normal and disomic sperm: Evidence that the extra chromosome 21 preferentially segregates with the Y chromosome

    Energy Technology Data Exchange (ETDEWEB)

    Griffin, D.K.; Millie, E.A.; Hassold, T.J. [Case Western Univ., Cleveland, OH (United States)]|[Univ. Hospitals of Cleveland, OH (United States)] [and others

    1996-11-01

    In humans, deviations from a 1:1 male:female ratio have been identified in both chromosomally normal and trisomic live births: among normal newborns there is a slight excess of males, among trisomy 18 live borns a large excess of females, and among trisomy 21 live borns an excess of males. These differences could arise from differential production of or fertilization by Y- or X-bearing sperm or from selection against male or female conceptions. To examine the proportion of Y- and X- bearing sperm in normal sperm and in sperm disomic for chromosomes 18 or 21, we used three-color FISH (to the X and Y and either chromosome 18 or chromosome 21) to analyze > 300,000 sperm from 24 men. In apparently normal sperm, the sex ratio was nearly 1:1 (148,074 Y-bearing to 148,657 X-bearing sperm), and the value was not affected by the age of the donor. Certain of the donors, however, had significant excesses of Y- or X-bearing sperm. In disomy 18 sperm, there were virtually identical numbers of Y- and X-bearing sperm; thus, the excess of females in trisomy 18 presumably is due to selection against male trisomic conceptions. In contrast, we observed 69 Y-bearing and 44 X-bearing sperm disomic for chromosome 21. This is consistent with previous molecular studies, which have identified an excess of males among paternally derived cases of trisomy 21, and suggests that some of the excess of males among Down syndrome individuals is attributable to a nondisjunctional mechanism in which the extra chromosome 21 preferentially segregates with the Y chromosome. 17 refs., 2 tabs.

  18. Multiple subunits of the Caenorhabditis elegans anaphase-promoting complex are required for chromosome segregation during meiosis I.

    OpenAIRE

    Davis, Edward S.; Wille, Lucia; Chestnut, Barry A.; Sadler, Penny L.; Shakes, Diane C; Golden, Andy

    2002-01-01

    Two genes, originally identified in genetic screens for Caenorhabditis elegans mutants that arrest in metaphase of meiosis I, prove to encode subunits of the anaphase-promoting complex or cyclosome (APC/C). RNA interference studies reveal that these and other APC/C subunits are essential for the segregation of chromosomal homologs during meiosis I. Further, chromosome segregation during meiosis I requires APC/C functions in addition to the release of sister chromatid cohesion.

  19. P190B RhoGAP Regulates Chromosome Segregation in Cancer Cells

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Melissa [Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617 (United States); Peddibhotla, Sirisha [Department of Molecular and Human Genetics, Baylor College of Medicine, John P. McGovern Campus, NABS-0250, Houston, TX 77030 (United States); McHenry, Peter [Department of Biology, Southwestern Adventist University, 100 W. Hillcrest, Keene, TX 76059 (United States); Chang, Peggy; Yochum, Zachary; Park, Ko Un; Sears, James Cooper; Vargo-Gogola, Tracy, E-mail: vargo-gogola.1@nd.edu [Department of Biochemistry and Molecular Biology and the Indiana University Simon Cancer Center, Indiana University School of Medicine, 1234 Notre Dame Avenue, South Bend, IN 46617 (United States)

    2012-04-25

    Rho GTPases are overexpressed and hyperactivated in many cancers, including breast cancer. Rho proteins, as well as their regulators and effectors, have been implicated in mitosis, and their altered expression promotes mitotic defects and aneuploidy. Previously, we demonstrated that p190B Rho GTPase activating protein (RhoGAP) deficiency inhibits ErbB2-induced mammary tumor formation in mice. Here we describe a novel role for p190B as a regulator of mitosis. We found that p190B localized to centrosomes during interphase and mitosis, and that it is differentially phosphorylated during mitosis. Knockdown of p190B expression in MCF-7 and Hela cells increased the incidence of aberrant microtubule-kinetochore attachments at metaphase, lagging chromosomes at anaphase, and micronucleation, all of which are indicative of aneuploidy. Cell cycle analysis of p190B deficient MCF-7 cells revealed a significant increase in apoptotic cells with a concomitant decrease in cells in G1 and S phase, suggesting that p190B deficient cells die at the G1 to S transition. Chemical inhibition of the Rac GTPase during mitosis reduced the incidence of lagging chromosomes in p190B knockdown cells to levels detected in control cells, suggesting that aberrant Rac activity in the absence of p190B promotes chromosome segregation defects. Taken together, these data suggest that p190B regulates chromosome segregation and apoptosis in cancer cells. We propose that disruption of mitosis may be one mechanism by which p190B deficiency inhibits tumorigenesis.

  20. P190B RhoGAP Regulates Chromosome Segregation in Cancer Cells

    International Nuclear Information System (INIS)

    Rho GTPases are overexpressed and hyperactivated in many cancers, including breast cancer. Rho proteins, as well as their regulators and effectors, have been implicated in mitosis, and their altered expression promotes mitotic defects and aneuploidy. Previously, we demonstrated that p190B Rho GTPase activating protein (RhoGAP) deficiency inhibits ErbB2-induced mammary tumor formation in mice. Here we describe a novel role for p190B as a regulator of mitosis. We found that p190B localized to centrosomes during interphase and mitosis, and that it is differentially phosphorylated during mitosis. Knockdown of p190B expression in MCF-7 and Hela cells increased the incidence of aberrant microtubule-kinetochore attachments at metaphase, lagging chromosomes at anaphase, and micronucleation, all of which are indicative of aneuploidy. Cell cycle analysis of p190B deficient MCF-7 cells revealed a significant increase in apoptotic cells with a concomitant decrease in cells in G1 and S phase, suggesting that p190B deficient cells die at the G1 to S transition. Chemical inhibition of the Rac GTPase during mitosis reduced the incidence of lagging chromosomes in p190B knockdown cells to levels detected in control cells, suggesting that aberrant Rac activity in the absence of p190B promotes chromosome segregation defects. Taken together, these data suggest that p190B regulates chromosome segregation and apoptosis in cancer cells. We propose that disruption of mitosis may be one mechanism by which p190B deficiency inhibits tumorigenesis

  1. Generation of meiomaps of genome-wide recombination and chromosome segregation in human oocytes.

    Science.gov (United States)

    Ottolini, Christian S; Capalbo, Antonio; Newnham, Louise; Cimadomo, Danilo; Natesan, Senthilkumar A; Hoffmann, Eva R; Ubaldi, Filippo M; Rienzi, Laura; Handyside, Alan H

    2016-07-01

    We have developed a protocol for the generation of genome-wide maps (meiomaps) of recombination and chromosome segregation for the three products of human female meiosis: the first and second polar bodies (PB1 and PB2) and the corresponding oocyte. PB1 is biopsied and the oocyte is artificially activated by exposure to calcium ionophore, after which PB2 is biopsied and collected with the corresponding oocyte. The whole genomes of the polar bodies and oocytes are amplified by multiple displacement amplification and, together with maternal genomic DNA, genotyped for ∼300,000 single-nucleotide polymorphisms (SNPs) genome-wide by microarray. Informative maternal heterozygous SNPs are phased using a haploid PB2 or oocyte as a reference. A simple algorithm is then used to identify the maternal haplotypes for each chromosome, in all of the products of meiosis for each oocyte. This allows mapping of crossovers and analysis of chromosome segregation patterns. The protocol takes a minimum of 3-5 d and requires a clinical embryologist with micromanipulation experience and a molecular biologist with basic bioinformatic skills. It has several advantages over previous methods; importantly, the use of artificial oocyte activation avoids the creation of embryos for research purposes. In addition, compared with next-generation sequencing, targeted SNP genotyping is cost-effective and it simplifies the bioinformatic analysis, as only one haploid reference sample is required to establish phase for maternal haplotyping. Finally, meiomapping is more informative than copy-number analysis alone for analysis of chromosome segregation patterns. Using this protocol, we have provided new insights that may lead to improvements in assisted reproduction for the treatment of infertility. PMID:27310263

  2. Bub3 is a spindle assembly checkpoint protein regulating chromosome segregation during mouse oocyte meiosis.

    Directory of Open Access Journals (Sweden)

    Mo Li

    Full Text Available In mitosis, the spindle assembly checkpoint (SAC prevents anaphase onset until all chromosomes have been attached to the spindle microtubules and aligned correctly at the equatorial metaphase plate. The major checkpoint proteins in mitosis consist of mitotic arrest-deficient (Mad1-3, budding uninhibited by benzimidazole (Bub1, Bub3, and monopolar spindle 1(Mps1. During meiosis, for the formation of a haploid gamete, two consecutive rounds of chromosome segregation occur with only one round of DNA replication. To pull homologous chromosomes to opposite spindle poles during meiosis I, both sister kinetochores of a homologue must face toward the same pole which is very different from mitosis and meiosis II. As a core member of checkpoint proteins, the individual role of Bub3 in mammalian oocyte meiosis is unclear. In this study, using overexpression and RNA interference (RNAi approaches, we analyzed the role of Bub3 in mouse oocyte meiosis. Our data showed that overexpressed Bub3 inhibited meiotic metaphase-anaphase transition by preventing homologous chromosome and sister chromatid segregations in meiosis I and II, respectively. Misaligned chromosomes, abnormal polar body and double polar bodies were observed in Bub3 knock-down oocytes, causing aneuploidy. Furthermore, through cold treatment combined with Bub3 overexpression, we found that overexpressed Bub3 affected the attachments of microtubules and kinetochores during metaphase-anaphase transition. We propose that as a member of SAC, Bub3 is required for regulation of both meiosis I and II, and is potentially involved in kinetochore-microtubule attachment in mammalian oocytes.

  3. Cell division patterns and chromosomal segregation defects in oral cancer stem cells.

    Science.gov (United States)

    Kaseb, Hatem O; Lewis, Dale W; Saunders, William S; Gollin, Susanne M

    2016-09-01

    Oral squamous cell carcinoma (OSCC) is a serious public health problem caused primarily by smoking and alcohol consumption or human papillomavirus. The cancer stem cell (CSC) theory posits that CSCs show unique characteristics, including self-renewal and therapeutic resistance. Examining biomarkers and other features of CSCs is critical to better understanding their biology. To this end, the results show that cellular SOX2 immunostaining correlates with other CSC biomarkers in OSCC cell lines and marks the rare CSC population. To assess whether CSC division patterns are symmetrical, resulting in two CSC, or asymmetrical, leading to one CSC and one cancer cell, cell size and fluorescence intensity of mitotic cells stained with SOX2 were analyzed. Asymmetrical SOX2 distribution in ≈25% of the mitoses analyzed was detected. Chromosomal instability, some of which is caused by chromosome segregation defects (CSDs), is a feature of cancer cells that leads to altered gene copy numbers. We compare chromosomal instability (as measured by CSDs) between CSCs (SOX2+) and non-CSCs (SOX2-) from the same OSCC cell lines. CSDs were more common in non-CSCs (SOX2-) than CSCs (SOX2+) and in symmetrical CSC (SOX2+) mitotic pairs than asymmetrical CSC (SOX2+/SOX2-) mitotic pairs. CSCs showed fewer and different types of CSDs after ionizing radiation treatment than non-CSCs. Overall, these data are the first to demonstrate both symmetrical and asymmetrical cell divisions with CSDs in OSCC CSC. Further, the results suggest that CSCs may undergo altered behavior, including therapeutic resistance as a result of chromosomal instability due to chromosome segregation defects. © 2016 Wiley Periodicals, Inc. PMID:27123539

  4. A Nucleoporin Docks Protein Phosphatase 1 to Direct Meiotic Chromosome Segregation and Nuclear Assembly.

    Science.gov (United States)

    Hattersley, Neil; Cheerambathur, Dhanya; Moyle, Mark; Stefanutti, Marine; Richardson, Amelia; Lee, Kian-Yong; Dumont, Julien; Oegema, Karen; Desai, Arshad

    2016-09-12

    During M-phase entry in metazoans with open mitosis, the concerted action of mitotic kinases disassembles nuclei and promotes assembly of kinetochores-the primary microtubule attachment sites on chromosomes. At M-phase exit, these major changes in cellular architecture must be reversed. Here, we show that the conserved kinetochore-localized nucleoporin MEL-28/ELYS docks the catalytic subunit of protein phosphatase 1 (PP1c) to direct kinetochore disassembly-dependent chromosome segregation during oocyte meiosis I and nuclear assembly during the transition from M phase to interphase. During oocyte meiosis I, MEL-28-PP1c disassembles kinetochores in a timely manner to promote elongation of the acentrosomal spindles that segregate homologous chromosomes. During nuclear assembly, MEL-28 recruits PP1c to the periphery of decondensed chromatin, where it directs formation of a functional nuclear compartment. Thus, a pool of phosphatase activity associated with a kinetochore-localized nucleoporin contributes to two key events that occur during M-phase exit in metazoans: kinetochore disassembly and nuclear reassembly. PMID:27623381

  5. SCF ensures meiotic chromosome segregation through a resolution of meiotic recombination intermediates.

    Directory of Open Access Journals (Sweden)

    Shin-ya Okamoto

    Full Text Available The SCF (Skp1-Cul1-F-box complex contributes to a variety of cellular events including meiotic cell cycle control, but its function during meiosis is not understood well. Here we describe a novel function of SCF/Skp1 in meiotic recombination and subsequent chromosome segregation. The skp1 temperature-sensitive mutant exhibited abnormal distribution of spindle microtubules in meiosis II, which turned out to originate from abnormal bending of the spindle in meiosis I. Bent spindles were reported in mitosis of this mutant, but it remained unknown how SCF could affect spindle morphology. We found that the meiotic bent spindle in skp1 cells was due to a hypertension generated by chromosome entanglement. The spindle bending was suppressed by inhibiting double strand break (DSB formation, indicating that the entanglement was generated by the meiotic recombination machinery. Consistently, Rhp51/Rad51-Rad22/Rad52 foci persisted until meiosis I in skp1 cells, proving accumulation of recombination intermediates. Intriguingly bent spindles were also observed in the mutant of Fbh1, an F-box protein containing the DNA helicase domain, which is involved in meiotic recombination. Genetic evidence suggested its cooperation with SCF/Skp1. Thus, SCF/Skp1 together with Fbh1 is likely to function in the resolution of meiotic recombination intermediates, thereby ensuring proper chromosome segregation.

  6. Regulatory cross-talk links Vibrio cholerae chromosome II replication and segregation.

    Directory of Open Access Journals (Sweden)

    Yoshiharu Yamaichi

    2011-07-01

    Full Text Available There is little knowledge of factors and mechanisms for coordinating bacterial chromosome replication and segregation. Previous studies have revealed that genes (and their products that surround the origin of replication (oriCII of Vibrio cholerae chromosome II (chrII are critical for controlling the replication and segregation of this chromosome. rctB, which flanks one side of oriCII, encodes a protein that initiates chrII replication; rctA, which flanks the other side of oriCII, inhibits rctB activity. The chrII parAB2 operon, which is essential for chrII partitioning, is located immediately downstream of rctA. Here, we explored how rctA exerts negative control over chrII replication. Our observations suggest that RctB has at least two DNA binding domains--one for binding to oriCII and initiating replication and the other for binding to rctA and thereby inhibiting RctB's ability to initiate replication. Notably, the inhibitory effect of rctA could be alleviated by binding of ParB2 to a centromere-like parS site within rctA. Furthermore, by binding to rctA, ParB2 and RctB inversely regulate expression of the parAB2 genes. Together, our findings suggest that fluctuations in binding of the partitioning protein ParB2 and the chrII initiator RctB to rctA underlie a regulatory network controlling both oriCII firing and the production of the essential chrII partitioning proteins. Thus, by binding both RctB and ParB2, rctA serves as a nexus for regulatory cross-talk coordinating chrII replication and segregation.

  7. Hormad1 mutation disrupts synaptonemal complex formation, recombination, and chromosome segregation in mammalian meiosis.

    Directory of Open Access Journals (Sweden)

    Yong-Hyun Shin

    2010-11-01

    Full Text Available Meiosis is unique to germ cells and essential for reproduction. During the first meiotic division, homologous chromosomes pair, recombine, and form chiasmata. The homologues connect via axial elements and numerous transverse filaments to form the synaptonemal complex. The synaptonemal complex is a critical component for chromosome pairing, segregation, and recombination. We previously identified a novel germ cell-specific HORMA domain encoding gene, Hormad1, a member of the synaptonemal complex and a mammalian counterpart to the yeast meiotic HORMA domain protein Hop1. Hormad1 is essential for mammalian gametogenesis as knockout male and female mice are infertile. Hormad1 deficient (Hormad1(-/ (- testes exhibit meiotic arrest in the early pachytene stage, and synaptonemal complexes cannot be visualized by electron microscopy. Hormad1 deficiency does not affect localization of other synaptonemal complex proteins, SYCP2 and SYCP3, but disrupts homologous chromosome pairing. Double stranded break formation and early recombination events are disrupted in Hormad1(-/ (- testes and ovaries as shown by the drastic decrease in the γH2AX, DMC1, RAD51, and RPA foci. HORMAD1 co-localizes with γH2AX to the sex body during pachytene. BRCA1, ATR, and γH2AX co-localize to the sex body and participate in meiotic sex chromosome inactivation and transcriptional silencing. Hormad1 deficiency abolishes γH2AX, ATR, and BRCA1 localization to the sex chromosomes and causes transcriptional de-repression on the X chromosome. Unlike testes, Hormad1(-/ (- ovaries have seemingly normal ovarian folliculogenesis after puberty. However, embryos generated from Hormad1(-/ (- oocytes are hyper- and hypodiploid at the 2 cell and 8 cell stage, and they arrest at the blastocyst stage. HORMAD1 is therefore a critical component of the synaptonemal complex that affects synapsis, recombination, and meiotic sex chromosome inactivation and transcriptional silencing.

  8. Interplay between Type 1A Topoisomerases and Gyrase in Chromosome Segregation in Escherichia coli

    OpenAIRE

    Usongo, Valentine; Tanguay, Cynthia; Nolent, Flora; Bessong, Jill Egbe; Drolet, Marc

    2013-01-01

    Escherichia coli possesses two type 1A topoisomerases, Topo I (topA) and Topo III (topB). Topo I relaxes excess negative supercoiling, and topA mutants can grow only in the presence of compensatory mechanisms, such as gyrase mutations. topB mutants grow as well as wild-type cells. In vitro, Topo III, but not Topo I, can efficiently decatenate DNA during replication. However, in vivo, a chromosome segregation defect is seen only when both type 1A topoisomerases are absent. Here we present expe...

  9. Kinesin 5B (KIF5B is required for progression through female meiosis and proper chromosomal segregation in mitotic cells.

    Directory of Open Access Journals (Sweden)

    Dawit Kidane

    Full Text Available The fidelity of chromosomal segregation during cell division is important to maintain chromosomal stability in order to prevent cancer and birth defects. Although several spindle-associated molecular motors have been shown to be essential for cell division, only a few chromosome arm-associated motors have been described. Here, we investigated the role of Kinesin 5b (Kif5b during female mouse meiotic cell development and mitotic cell division. RNA interference (RNAi-mediated silencing of Kif5b in mouse oocytes induced significant delay in germinal vesicle breakdown (GVBD and failure in extrusion of the first polar body (PBE. In mitotic cells, knockdown of Kif5b leads to centrosome amplification and a chromosomal segregation defect. These data suggest that KIF5B is critical in suppressing chromosomal instability at the early stages of female meiotic cell development and mitotic cell division.

  10. Kinesin 5B (KIF5B) is required for progression through female meiosis and proper chromosomal segregation in mitotic cells.

    Science.gov (United States)

    Kidane, Dawit; Sakkas, Denny; Nottoli, Timothy; McGrath, James; Sweasy, Joann B

    2013-01-01

    The fidelity of chromosomal segregation during cell division is important to maintain chromosomal stability in order to prevent cancer and birth defects. Although several spindle-associated molecular motors have been shown to be essential for cell division, only a few chromosome arm-associated motors have been described. Here, we investigated the role of Kinesin 5b (Kif5b) during female mouse meiotic cell development and mitotic cell division. RNA interference (RNAi)-mediated silencing of Kif5b in mouse oocytes induced significant delay in germinal vesicle breakdown (GVBD) and failure in extrusion of the first polar body (PBE). In mitotic cells, knockdown of Kif5b leads to centrosome amplification and a chromosomal segregation defect. These data suggest that KIF5B is critical in suppressing chromosomal instability at the early stages of female meiotic cell development and mitotic cell division.

  11. Spindle checkpoint-independent inhibition of mitotic chromosome segregation by Drosophila Mps1.

    Science.gov (United States)

    Althoff, Friederike; Karess, Roger E; Lehner, Christian F

    2012-06-01

    Monopolar spindle 1 (Mps1) is essential for the spindle assembly checkpoint (SAC), which prevents anaphase onset in the presence of misaligned chromosomes. Moreover, Mps1 kinase contributes in a SAC-independent manner to the correction of erroneous initial attachments of chromosomes to the spindle. Our characterization of the Drosophila homologue reveals yet another SAC-independent role. As in yeast, modest overexpression of Drosophila Mps1 is sufficient to delay progression through mitosis during metaphase, even though chromosome congression and metaphase alignment do not appear to be affected. This delay in metaphase depends on the SAC component Mad2. Although Mps1 overexpression in mad2 mutants no longer causes a metaphase delay, it perturbs anaphase. Sister kinetochores barely move apart toward spindle poles. However, kinetochore movements can be restored experimentally by separase-independent resolution of sister chromatid cohesion. We propose therefore that Mps1 inhibits sister chromatid separation in a SAC-independent manner. Moreover, we report unexpected results concerning the requirement of Mps1 dimerization and kinase activity for its kinetochore localization in Drosophila. These findings further expand Mps1's significance for faithful mitotic chromosome segregation and emphasize the importance of its careful regulation.

  12. [Effect of gametocidal chromosome 4S' on the phenotype segregation ratio in genetic analysis of common wheat lines].

    Science.gov (United States)

    Vdovichenko, Zh V; Antoniuk, M Z; Ternovskaia, T K

    2003-01-01

    Using experimental data on genetic analysis of introgressive lines for the character "hairy leaf sheath" controlled by the "cuckoo" chromosome 4S1, the algorithm for calculation of the theoretical segregation ratio in F2 was developed. Segregation distortion is caused by non-viability of the majority of gametes lacking the chromosome 4S1. The frequency of functioning gametes without the chromosome 4S1 is determined by the probability p versus the theoretically expected ratio 7 nonviable: 9 viable ones. Since segregation involves two characters, gamete viability and hairiness, the ratio 15 hairy: 1 hairless was used as a basis for search of the frequency p by maximum-likelihood method using 16 populations F2 from crossing the lines differing in the character studied. PMID:14650327

  13. Long G2 accumulates recombination intermediates and disturbs chromosome segregation at dysfunction telomere in Schizosaccharomyces pombe

    Energy Technology Data Exchange (ETDEWEB)

    Habib, Ahmed G.K.; Masuda, Kenta; Yukawa, Masashi; Tsuchiya, Eiko [Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Ueno, Masaru, E-mail: scmueno@hiroshima-u.ac.jp [Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan); Research Center for the Mathematics on Chromatin Live Dynamics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530 (Japan)

    2015-08-14

    Protection of telomere (Pot1) is a single-stranded telomere binding protein which is essential for chromosome ends protection. Fission yeast Rqh1 is a member of RecQ helicases family which has essential roles in the maintenance of genomic stability and regulation of homologous recombination. Double mutant between fission yeast pot1Δ and rqh1 helicase dead (rqh1-hd) maintains telomere by homologous recombination. In pot1Δ rqh1-hd double mutant, recombination intermediates accumulate near telomere which disturb chromosome segregation and make cells sensitive to microtubule inhibitors thiabendazole (TBZ). Deletion of chk1{sup +} or mutation of its kinase domain shortens the G2 of pot1Δ rqh1-hd double mutant and suppresses both the accumulation of recombination intermediates and the TBZ sensitivity of that double mutant. In this study, we asked whether the long G2 is the reason for the TBZ sensitivity of pot1Δ rqh1-hd double mutant. We found that shortening the G2 of pot1Δ rqh1-hd double mutant by additional mutations of wee1 and mik1 or gain of function mutation of Cdc2 suppresses both the accumulation of recombination intermediates and the TBZ sensitivity of pot1Δ rqh1-hd double mutant. Our results suggest that long G2 of pot1Δ rqh1-hd double mutant may allow time for the accumulation of recombination intermediates which disturb chromosome segregation and make cells sensitive to TBZ. - Ηighlights: • We show link between long G2 and accumulation of toxic recombination intermediates. • Accumulation of recombination intermediates at telomere results in TBZ sensitivity. • Activation of DNA damage checkpoint worsens cells' viability in presence of TBZ.

  14. Distance segregation of sex chromosomes in crane-fly spermatocytes studied using laser microbeam irradiations.

    Science.gov (United States)

    Forer, Arthur; Ferraro-Gideon, Jessica; Berns, Michael

    2013-10-01

    Univalent sex chromosomes in crane-fly spermatocytes have kinetochore spindle fibres to each spindle pole (amphitelic orientation) from metaphase throughout anaphase. The univalents segregate in anaphase only after the autosomes approach the poles. As each univalent moves in anaphase, one spindle fibre shortens and the other spindle fibre elongates. To test whether the directionality of force production is fixed at anaphase, that is, whether one spindle fibre can only elongate and the other only shorten, we cut univalents in half with a laser microbeam, to create two chromatids. In both sex-chromosome metaphase and sex-chromosome anaphase, the two chromatids that were formed moved to opposite poles (to the poles to which their fibre was attached) at speeds about the same as autosomes, much faster than the usual speeds of univalent movements. Since the chromatids moved to the pole to which they were attached, independent of the direction to which the univalent as a whole was moving, the spindle fibre that normally elongates in anaphase still is able to shorten and produce force towards the pole when allowed (or caused) to do so. PMID:23315093

  15. Cyc17, a meiosis-specific cyclin, is essential for anaphase initiation and chromosome segregation in Tetrahymena thermophila.

    Science.gov (United States)

    Yan, Guan-Xiong; Dang, Huai; Tian, Miao; Zhang, Jing; Shodhan, Anura; Ning, Ying-Zhi; Xiong, Jie; Miao, Wei

    2016-07-17

    Although the role of cyclins in controlling nuclear division is well established, their function in ciliate meiosis remains unknown. In ciliates, the cyclin family has undergone massive expansion which suggests that diverse cell cycle systems exist, and this warrants further investigation. A screen for cyclins in the model ciliate Tetrahymena thermophila showed that there are 34 cyclins in this organism. Only 1 cyclin, Cyc17, contains the complete cyclin core and is specifically expressed during meiosis. Deletion of CYC17 led to meiotic arrest at the diakinesis-like metaphase I stage. Expression of genes involved in DNA metabolism and chromosome organization (chromatin remodeling and basic chromosomal structure) was repressed in cyc17 knockout matings. Further investigation suggested that Cyc17 is involved in regulating spindle pole attachment, and is thus essential for chromosome segregation at meiosis. These findings suggest a simple model in which chromosome segregation is influenced by Cyc17. PMID:27192402

  16. A defined terminal region of the E. coli chromosome shows late segregation and high FtsK activity.

    Directory of Open Access Journals (Sweden)

    Marie Deghorain

    Full Text Available BACKGROUND: The FtsK DNA-translocase controls the last steps of chromosome segregation in E. coli. It translocates sister chromosomes using the KOPS DNA motifs to orient its activity, and controls the resolution of dimeric forms of sister chromosomes by XerCD-mediated recombination at the dif site and their decatenation by TopoIV. METHODOLOGY: We have used XerCD/dif recombination as a genetic trap to probe the interaction of FtsK with loci located in different regions of the chromosome. This assay revealed that the activity of FtsK is restricted to a ∼400 kb terminal region of the chromosome around the natural position of the dif site. Preferential interaction with this region required the tethering of FtsK to the division septum via its N-terminal domain as well as its translocation activity. However, the KOPS-recognition activity of FtsK was not required. Displacement of replication termination outside the FtsK high activity region had no effect on FtsK activity and deletion of a part of this region was not compensated by its extension to neighbouring regions. By observing the fate of fluorescent-tagged loci of the ter region, we found that segregation of the FtsK high activity region is delayed compared to that of its adjacent regions. SIGNIFICANCE: Our results show that a restricted terminal region of the chromosome is specifically dedicated to the last steps of chromosome segregation and to their coupling with cell division by FtsK.

  17. Non-SMC condensin I complex proteins control chromosome segregation and survival of proliferating cells in the zebrafish neural retina

    Directory of Open Access Journals (Sweden)

    Harris William A

    2009-07-01

    Full Text Available Abstract Background The condensation of chromosomes and correct sister chromatid segregation during cell division is an essential feature of all proliferative cells. Structural maintenance of chromosomes (SMC and non-SMC proteins form the condensin I complex and regulate chromosome condensation and segregation during mitosis. However, due to the lack of appropriate mutants, the function of the condensin I complex during vertebrate development has not been described. Results Here, we report the positional cloning and detailed characterization of retinal phenotypes of a zebrafish mutation at the cap-g locus. High resolution live imaging reveals that the progression of mitosis between prometa- to telophase is delayed and that sister chromatid segregation is impaired upon loss of CAP-G. CAP-G associates with chromosomes between prometa- and telophase of the cell cycle. Loss of the interaction partners CAP-H and CAP-D2 causes cytoplasmic mislocalization of CAP-G throughout mitosis. DNA content analysis reveals increased genomic imbalances upon loss of non-SMC condensin I subunits. Within the retina, loss of condensin I function causes increased rates of apoptosis among cells within the proliferative ciliary marginal zone (CMZ whereas postmitotic retinal cells are viable. Inhibition of p53-mediated apoptosis partially rescues cell numbers in cap-g mutant retinae and allows normal layering of retinal cell types without alleviating their aberrant nuclear sizes. Conclusion Our findings indicate that the condensin I complex is particularly important within rapidly amplifying progenitor cell populations to ensure faithful chromosome segregation. In contrast, differentiation of postmitotic retinal cells is not impaired upon polyploidization.

  18. Segregation of chromosome arms in growing and non-growing Escherichia coli cells

    DEFF Research Database (Denmark)

    Woldringh, Conrad L.; Hansen, Flemming G.; Vischer, Norbert O. E.;

    2015-01-01

    In slow-growing Escherichia coli cells the chromosome is organized with its left (L) and right (R) arms lying separated in opposite halves of the nucleoid and with the origin (0) in-between, giving the pattern L-O-R. During replication one of the arms has to pass the other to obtain the same...... organization in the daughter cells: L-O-R L-O-R. To determine the movement of arms during segregation six strains were constructed carrying three colored loci: the left and right arms were labeled with red and cyan fluorescent-proteins, respectively, on loci symmetrically positioned at different distances from...... that the movement of arms is not a growth-sustained process, but may result from DNA synthesis itself. The distances between loci on different arms (LR-distances) and between duplicated loci (LL- or RR-distances) as a function of their distance from the origin, indicate that in slow-growing cells DNA is organized...

  19. Three Different Pathways Prevent Chromosome Segregation in the Presence of DNA Damage or Replication Stress in Budding Yeast.

    Directory of Open Access Journals (Sweden)

    Gloria Palou

    2015-09-01

    Full Text Available A surveillance mechanism, the S phase checkpoint, blocks progression into mitosis in response to DNA damage and replication stress. Segregation of damaged or incompletely replicated chromosomes results in genomic instability. In humans, the S phase checkpoint has been shown to constitute an anti-cancer barrier. Inhibition of mitotic cyclin dependent kinase (M-CDK activity by Wee1 kinases is critical to block mitosis in some organisms. However, such mechanism is dispensable in the response to genotoxic stress in the model eukaryotic organism Saccharomyces cerevisiae. We show here that the Wee1 ortholog Swe1 does indeed inhibit M-CDK activity and chromosome segregation in response to genotoxic insults. Swe1 dispensability in budding yeast is the result of a redundant control of M-CDK activity by the checkpoint kinase Rad53. In addition, our results indicate that Swe1 is an effector of the checkpoint central kinase Mec1. When checkpoint control on M-CDK and on Pds1/securin stabilization are abrogated, cells undergo aberrant chromosome segregation.

  20. Three Different Pathways Prevent Chromosome Segregation in the Presence of DNA Damage or Replication Stress in Budding Yeast.

    Science.gov (United States)

    Palou, Gloria; Palou, Roger; Zeng, Fanli; Vashisht, Ajay A; Wohlschlegel, James A; Quintana, David G

    2015-09-01

    A surveillance mechanism, the S phase checkpoint, blocks progression into mitosis in response to DNA damage and replication stress. Segregation of damaged or incompletely replicated chromosomes results in genomic instability. In humans, the S phase checkpoint has been shown to constitute an anti-cancer barrier. Inhibition of mitotic cyclin dependent kinase (M-CDK) activity by Wee1 kinases is critical to block mitosis in some organisms. However, such mechanism is dispensable in the response to genotoxic stress in the model eukaryotic organism Saccharomyces cerevisiae. We show here that the Wee1 ortholog Swe1 does indeed inhibit M-CDK activity and chromosome segregation in response to genotoxic insults. Swe1 dispensability in budding yeast is the result of a redundant control of M-CDK activity by the checkpoint kinase Rad53. In addition, our results indicate that Swe1 is an effector of the checkpoint central kinase Mec1. When checkpoint control on M-CDK and on Pds1/securin stabilization are abrogated, cells undergo aberrant chromosome segregation. PMID:26332045

  1. Segregation of chromosome arms in growing and non-growing Escherichia coli cells

    Directory of Open Access Journals (Sweden)

    Conrad L. Woldringh

    2015-05-01

    Full Text Available In slow-growing Escherichia coli cells the chromosome is organized with its left (L and right (R arms lying separated in opposite halves of the nucleoid and with the origin (O in-between, giving the pattern L-O-R. During replication one of the arms has to pass the other to obtain the same organization in the daughter cells: L-O-R L-O-R. To determine the movement of arms during segregation six strains were constructed carrying three coloured loci: the left and right arms were labeled with red and cyan fluorescent-proteins, respectively, on loci symmetrically positioned at different distances from the central origin, which was labeled with green-fluorescent protein. In non-replicating cells with the predominant spot pattern L-O-R, initiation of replication first resulted in a L-O-O-R pattern, soon changing to O-L-R-O. After replication of the arms the predominant spot patterns were, L-O-R L-O-R, O-R-L R-O-L or O-L-R L-O-R indicating that one or both arms passed an origin and the other arm. To study the driving force for these movements cell growth was inhibited with rifampicin allowing run-off DNA synthesis. Similar spot patterns were obtained in growing and non-growing cells, indicating that the movement of arms is not a growth-sustained process, but may result from DNA synthesis itself. The distances between loci on different arms (LR-distances and between duplicated loci (LL- or RR-distances as a function of their distance from the origin, indicate that in slow-growing cells DNA is organized according to the so-called sausage model and not accordingto the doughnut model.

  2. X chromosome-linked and mitochondrial gene control of Leber hereditary optic neuropathy: Evidence from segregation analysis for dependence on X chromosome inactivation

    Energy Technology Data Exchange (ETDEWEB)

    Xiangdong Bu; Rotter, J.I. (Cedars-Sinai Medical Center, Los Angeles, CA (United States) Univ. of California, Los Angeles (United States))

    1991-09-15

    Leber hereditary optic neuropathy (LHON) has been shown to involve mutation(s) of mitochondrial DNA, yet there remain several confusing aspects of its inheritance not explained by mitochondrial inheritance alone, including male predominance, reduced penetrance, and a later age of onset in females. By extending segregation analysis methods to disorders that involve both a mitochondrial and a nuclear gene locus, the authors show that the available pedigree data for LHON are most consistent with a two-locus disorder, with one responsible gene being mitochondrial and the other nuclear and X chromosome-linked. Furthermore, they have been able to extend the two-locus analytic method and demonstrate that a proportion of affected females are likely heterozygous at the X chromosome-linked locus and are affected due to unfortunate X chromosome inactivation, thus providing an explanation for the later age of onset in females. The estimated penetrance for a heterozygous female is 0.11{plus minus}0.02. The calculated frequency of the X chromosome-linked gene for LHON is 0.l08. Among affected females, 60% are expected to be heterozygous, and the remainder are expected to be homozygous at the responsible X chromosome-linked locus.

  3. Identification and Characterization of Segregation Distortion Loci Along Chromosome 5B in Tetraploid Wheat

    Science.gov (United States)

    Segregation distortion genes are widespread in plants and animals and function by their effect on competition among gametes for preferential fertilization. In this study, we evaluated the segregation distortion of molecular markers in multiple reciprocal backcross populations derived from unique cy...

  4. The Argonaute CSR-1 and its 22G-RNA co-factors target germline genes and are required for holocentric chromosome segregation

    OpenAIRE

    Claycomb, Julie M.; Batista, Pedro J; Pang, Ka Ming; Gu, Weifeng; Vasale, Jessica J.; van Wolfswinkel, Josien C.; Chaves, Daniel A.; Shirayama, Masaki; Mitani, Shohei; Ketting, René F.; Conte, Darryl; Mello, Craig C

    2009-01-01

    RNAi-related pathways regulate diverse processes, from developmental timing to transposon silencing. Here, we show that in C. elegans the Argonaute CSR-1, the RNA-dependent RNA polymerase EGO-1, the Dicer-related helicase DRH-3, and the Tudor-domain protein EKL-1 localize to chromosomes and are required for proper chromosome segregation. In the absence of these factors chromosomes fail to align at the metaphase plate and kinetochores do not orient to opposing spindle poles. Surprisingly, the ...

  5. Mutation of histone H3 serine 86 disrupts GATA factor Ams2 expression and precise chromosome segregation in fission yeast.

    Science.gov (United States)

    Lim, Kim Kiat; Ong, Terenze Yao Rui; Tan, Yue Rong; Yang, Eugene Guorong; Ren, Bingbing; Seah, Kwi Shan; Yang, Zhe; Tan, Tsu Soo; Dymock, Brian W; Chen, Ee Sin

    2015-01-01

    Eukaryotic genomes are packed into discrete units, referred to as nucleosomes, by organizing around scaffolding histone proteins. The interplay between these histones and the DNA can dynamically regulate the function of the chromosomal domain. Here, we interrogated the function of a pair of juxtaposing serine residues (S86 and S87) that reside within the histone fold of histone H3. We show that fission yeast cells expressing a mutant histone H3 disrupted at S86 and S87 (hht2-S86AS87A) exhibited unequal chromosome segregation, disrupted transcriptional silencing of centromeric chromatin, and reduced expression of Ams2, a GATA-factor that regulates localization of the centromere-specific histone H3 variant CENP-A. We found that overexpression of ams2(+) could suppress the chromosome missegregation phenotype that arose in the hht2-S86AS87A mutant. We further demonstrate that centromeric localization of SpCENP-A(cnp1-1) was significantly compromised in hht2-S86AS87A, suggesting synergism between histone H3 and the centromere-targeting domain of SpCENP-A. Taken together, our work presents evidence for an uncharacterized serine residue in fission yeast histone H3 that affects centromeric integrity via regulating the expression of the SpCENP-A-localizing Ams2 protein. [173/200 words]. PMID:26369364

  6. The role of meiotic cohesin REC8 in chromosome segregation in {gamma} irradiation-induced endopolyploid tumour cells

    Energy Technology Data Exchange (ETDEWEB)

    Erenpreisa, Jekaterina [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Cragg, Mark S. [Tenovus Laboratory, Cancer Sciences Division, Southampton University School of Medicine, General Hospital, Southampton SO16 6YD (United Kingdom); Salmina, Kristine [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Hausmann, Michael [Kirchhoff Inst. fuer Physik, Univ. of Heidelberg, D-69120 Heidelberg (Germany); Scherthan, Harry, E-mail: scherth@web.de [Inst. fuer Radiobiologie der Bundeswehr in Verbindung mit der Univ. Ulm, D-80937 Munich (Germany); MPI for Molec. Genetics, 14195 Berlin (Germany)

    2009-09-10

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  7. PP2A(Cdc55)'s role in reductional chromosome segregation during achiasmate meiosis in budding yeast is independent of its FEAR function.

    Science.gov (United States)

    Kerr, Gary W; Wong, Jin Huei; Arumugam, Prakash

    2016-01-01

    PP2A(Cdc55) is a highly conserved serine-threonine protein phosphatase that is involved in diverse cellular processes. In budding yeast, meiotic cells lacking PP2A(Cdc55) activity undergo a premature exit from meiosis I which results in a failure to form bipolar spindles and divide nuclei. This defect is largely due to its role in negatively regulating the Cdc Fourteen Early Anaphase Release (FEAR) pathway. PP2A(Cdc55) prevents nucleolar release of the Cdk (Cyclin-dependent kinase)-antagonising phosphatase Cdc14 by counteracting phosphorylation of the nucleolar protein Net1 by Cdk. CDC55 was identified in a genetic screen for monopolins performed by isolating suppressors of spo11Δ spo12Δ lethality suggesting that Cdc55 might have a role in meiotic chromosome segregation. We investigated this possibility by isolating cdc55 alleles that suppress spo11Δ spo12Δ lethality and show that this suppression is independent of PP2A(Cdc55)'s FEAR function. Although the suppressor mutations in cdc55 affect reductional chromosome segregation in the absence of recombination, they have no effect on chromosome segregation during wild type meiosis. We suggest that Cdc55 is required for reductional chromosome segregation during achiasmate meiosis and this is independent of its FEAR function. PMID:27455870

  8. PP2ACdc55’s role in reductional chromosome segregation during achiasmate meiosis in budding yeast is independent of its FEAR function

    Science.gov (United States)

    Kerr, Gary W.; Wong, Jin Huei; Arumugam, Prakash

    2016-01-01

    PP2ACdc55 is a highly conserved serine-threonine protein phosphatase that is involved in diverse cellular processes. In budding yeast, meiotic cells lacking PP2ACdc55 activity undergo a premature exit from meiosis I which results in a failure to form bipolar spindles and divide nuclei. This defect is largely due to its role in negatively regulating the Cdc Fourteen Early Anaphase Release (FEAR) pathway. PP2ACdc55 prevents nucleolar release of the Cdk (Cyclin-dependent kinase)-antagonising phosphatase Cdc14 by counteracting phosphorylation of the nucleolar protein Net1 by Cdk. CDC55 was identified in a genetic screen for monopolins performed by isolating suppressors of spo11Δ spo12Δ lethality suggesting that Cdc55 might have a role in meiotic chromosome segregation. We investigated this possibility by isolating cdc55 alleles that suppress spo11Δ spo12Δ lethality and show that this suppression is independent of PP2ACdc55’s FEAR function. Although the suppressor mutations in cdc55 affect reductional chromosome segregation in the absence of recombination, they have no effect on chromosome segregation during wild type meiosis. We suggest that Cdc55 is required for reductional chromosome segregation during achiasmate meiosis and this is independent of its FEAR function. PMID:27455870

  9. Intact Cohesion, Anaphase, and Chromosome Segregation in Human Cells Harboring Tumor-Derived Mutations in STAG2.

    Directory of Open Access Journals (Sweden)

    Jung-Sik Kim

    2016-02-01

    Full Text Available Somatic mutations of the cohesin complex subunit STAG2 are present in diverse tumor types. We and others have shown that STAG2 inactivation can lead to loss of sister chromatid cohesion and alterations in chromosome copy number in experimental systems. However, studies of naturally occurring human tumors have demonstrated little, if any, correlation between STAG2 mutational status and aneuploidy, and have further shown that STAG2-deficient tumors are often euploid. In an effort to provide insight into these discrepancies, here we analyze the effect of tumor-derived STAG2 mutations on the protein composition of cohesin and the expected mitotic phenotypes of STAG2 mutation. We find that many mutant STAG2 proteins retain their ability to interact with cohesin; however, the presence of mutant STAG2 resulted in a reduction in the ability of regulatory subunits WAPL, PDS5A, and PDS5B to interact with the core cohesin ring. Using AAV-mediated gene targeting, we then introduced nine tumor-derived mutations into the endogenous allele of STAG2 in cultured human cells. While all nonsense mutations led to defects in sister chromatid cohesion and a subset induced anaphase defects, missense mutations behaved like wild-type in these assays. Furthermore, only one of nine tumor-derived mutations tested induced overt alterations in chromosome counts. These data indicate that not all tumor-derived STAG2 mutations confer defects in cohesion, chromosome segregation, and ploidy, suggesting that there are likely to be other functional effects of STAG2 inactivation in human cancer cells that are relevant to cancer pathogenesis.

  10. Dynamic and Stable Cohesins Regulate Synaptonemal Complex Assembly and Chromosome Segregation.

    Science.gov (United States)

    Gyuricza, Mercedes R; Manheimer, Kathryn B; Apte, Vandana; Krishnan, Badri; Joyce, Eric F; McKee, Bruce D; McKim, Kim S

    2016-07-11

    Assembly of the synaptonemal complex (SC) in Drosophila depends on two independent pathways defined by the chromosome axis proteins C(2)M and ORD. Because C(2)M encodes a Kleisin-like protein and ORD is required for sister-chromatid cohesion, we tested the hypothesis that these two SC assembly pathways depend on two cohesin complexes. Through single- and double-mutant analysis to study the mitotic cohesion proteins Stromalin (SA) and Nipped-B (SCC2) in meiosis, we provide evidence that there are at least two meiosis-specific cohesin complexes. One complex depends on C(2)M, SA, and Nipped-B. Despite the presence of mitotic cohesins SA and Nipped-B, this pathway has only a minor role in meiotic sister-centromere cohesion and is primarily required for homolog interactions. C(2)M is continuously incorporated into pachytene chromosomes even though SC assembly is complete. In contrast, the second complex, which depends on meiosis-specific proteins SOLO, SUNN, and ORD is required for sister-chromatid cohesion, localizes to the centromeres and is not incorporated during prophase. Our results show that the two cohesin complexes have unique functions and are regulated differently. Multiple cohesin complexes may provide the diversity of activities required by the meiotic cell. For example, a dynamic complex may allow the chromosomes to regulate meiotic recombination, and a stable complex may be required for sister-chromatid cohesion. PMID:27291057

  11. High frequency of submicroscopic chromosomal imbalances in patients with syndromic craniosynostosis detected by a combined approach of microsatellite segregation analysis, multiplex ligation-dependent probe amplification and array-based comparative genome hybridisation.

    NARCIS (Netherlands)

    Jehee, F.S.; Krepischi-Santos, A.C.; Rocha, K.M.; Cavalcanti, D.P.; Kim, C.A.; Bertola, D.R.; Alonso, L.G.; D'Angelo, C.S.; Mazzeu, J.F.; Froyen, G.; Lugtenberg, D.; Vianna-Morgante, A.M.; Rosenberg, C.; Passos-Bueno, M.R.

    2008-01-01

    We present the first comprehensive study, to our knowledge, on genomic chromosomal analysis in syndromic craniosynostosis. In total, 45 patients with craniosynostotic disorders were screened with a variety of methods including conventional karyotype, microsatellite segregation analysis, subtelomeric

  12. Risk evaluation of carriers with chromosome reciprocal translocation t(7;13)(q34;q13) and concomitant meiotic segregation analyzed by FISH on ejaculated spermatozoa.

    Science.gov (United States)

    Midro, Alina T; Wiland, Ewa; Panasiuk, Barbara; Leśniewicz, Ryszard; Kurpisz, Maciej

    2006-02-01

    We performed the segregation analysis of a relatively large pedigree of t(7;13)(q34;q13) carriers together with the sperm karyotype analysis of the one carrier using a tri-color fluorescence in situ hybridization (FISH) method. The risk assessments for unfavorable pregnancy outcomes in a series of 36 pregnancies in eight reciprocal chromosome translocation (RCT) couples of carriers were estimated directly from a pedigree after ascertainment correction. The individual probability rate for unbalanced child was predicted according to Stengel-Rutkowski and co-workers. The unbalanced karyotypes in the form of monosomy 7q34-->qter and trisomy 13q13-->qter were detected among stillborn/early death newborns with holoprosencephaly (HPE), cyclopia and other malformations. Based on clinical description of unkaryotyped stillbirth progeny, it can be assumed that the phenotype distinctions were connected with the unbalanced karyotype from 2:2 segregation (monosomy 7q with trisomy 13q) and 3:1 segregation as interchange trisomy 13 (Patau syndrome). Probability rates for miscarriages, stillbirth/early death were 12.9 +/- 6% (4/31) and 29 +/- 8.2% (9/31), respectively. The results of the meiotic segregation pattern indicated the rate of unbalanced spermatozoa for about 60%, with the unusual high rate (29.4%) of 3:1 segregant (i.e., 13.4% of the tertiary segregation and 16% of the interchange segregation). Adjacent-1 segregation followed with 23.5% and adjacent-2 followed with 7.2% of analyzed spermatozoa. The high rate of unbalanced gametes in comparison to the number of stillborn/early death and miscarriages detected in pedigree suggests a strong selection against unbalanced chromosomal constitutions during fetal development. It corresponds to a very small probability rate (about 0.3%) of viable unbalanced progeny from 3:1 meiotic segregation predicted for maternal carriers. This knowledge can be used in genetic counseling of families with similar RCT ascertained in a different

  13. Mitotic spindle defects and chromosome mis-segregation induced by LDL/cholesterol-implications for Niemann-Pick C1, Alzheimer's disease, and atherosclerosis.

    Directory of Open Access Journals (Sweden)

    Antoneta Granic

    Full Text Available Elevated low-density lipoprotein (LDL-cholesterol is a risk factor for both Alzheimer's disease (AD and Atherosclerosis (CVD, suggesting a common lipid-sensitive step in their pathogenesis. Previous results show that AD and CVD also share a cell cycle defect: chromosome instability and up to 30% aneuploidy-in neurons and other cells in AD and in smooth muscle cells in atherosclerotic plaques in CVD. Indeed, specific degeneration of aneuploid neurons accounts for 90% of neuronal loss in AD brain, indicating that aneuploidy underlies AD neurodegeneration. Cell/mouse models of AD develop similar aneuploidy through amyloid-beta (Aß inhibition of specific microtubule motors and consequent disruption of mitotic spindles. Here we tested the hypothesis that, like upregulated Aß, elevated LDL/cholesterol and altered intracellular cholesterol homeostasis also causes chromosomal instability. Specifically we found that: 1 high dietary cholesterol induces aneuploidy in mice, satisfying the hypothesis' first prediction, 2 Niemann-Pick C1 patients accumulate aneuploid fibroblasts, neurons, and glia, demonstrating a similar aneugenic effect of intracellular cholesterol accumulation in humans 3 oxidized LDL, LDL, and cholesterol, but not high-density lipoprotein (HDL, induce chromosome mis-segregation and aneuploidy in cultured cells, including neuronal precursors, indicating that LDL/cholesterol directly affects the cell cycle, 4 LDL-induced aneuploidy requires the LDL receptor, but not Aß, showing that LDL works differently than Aß, with the same end result, 5 cholesterol treatment disrupts the structure of the mitotic spindle, providing a cell biological mechanism for its aneugenic activity, and 6 ethanol or calcium chelation attenuates lipoprotein-induced chromosome mis-segregation, providing molecular insights into cholesterol's aneugenic mechanism, specifically through its rigidifying effect on the cell membrane, and potentially explaining why ethanol

  14. Phosphorylation of Mycobacterium tuberculosis ParB participates in regulating the ParABS chromosome segregation system.

    Directory of Open Access Journals (Sweden)

    Grégory Baronian

    Full Text Available Here, we present for the first time that Mycobacterium tuberculosis ParB is phosphorylated by several mycobacterial Ser/Thr protein kinases in vitro. ParB and ParA are the key components of bacterial chromosome segregation apparatus. ParB is a cytosolic conserved protein that binds specifically to centromere-like DNA parS sequences and interacts with ParA, a weak ATPase required for its proper localization. Mass spectrometry identified the presence of ten phosphate groups, thus indicating that ParB is phosphorylated on eight threonines, Thr32, Thr41, Thr53, Thr110, Thr195, and Thr254, Thr300, Thr303 as well as on two serines, Ser5 and Ser239. The phosphorylation sites were further substituted either by alanine to prevent phosphorylation or aspartate to mimic constitutive phosphorylation. Electrophoretic mobility shift assays revealed a drastic inhibition of DNA-binding by ParB phosphomimetic mutant compared to wild type. In addition, bacterial two-hybrid experiments showed a loss of ParA-ParB interaction with the phosphomimetic mutant, indicating that phosphorylation is regulating the recruitment of the partitioning complex. Moreover, fluorescence microscopy experiments performed in the surrogate Mycobacterium smegmatis ΔparB strain revealed that in contrast to wild type Mtb ParB, which formed subpolar foci similar to M. smegmatis ParB, phoshomimetic Mtb ParB was delocalized. Thus, our findings highlight a novel regulatory role of the different isoforms of ParB representing a molecular switch in localization and functioning of partitioning protein in Mycobacterium tuberculosis.

  15. Multipolar spindle pole coalescence is a major source of kinetochore mis-attachment and chromosome mis-segregation in cancer cells.

    Directory of Open Access Journals (Sweden)

    William T Silkworth

    Full Text Available Many cancer cells display a CIN (Chromosome Instability phenotype, by which they exhibit high rates of chromosome loss or gain at each cell cycle. Over the years, a number of different mechanisms, including mitotic spindle multipolarity, cytokinesis failure, and merotelic kinetochore orientation, have been proposed as causes of CIN. However, a comprehensive theory of how CIN is perpetuated is still lacking. We used CIN colorectal cancer cells as a model system to investigate the possible cellular mechanism(s underlying CIN. We found that CIN cells frequently assembled multipolar spindles in early mitosis. However, multipolar anaphase cells were very rare, and live-cell experiments showed that almost all CIN cells divided in a bipolar fashion. Moreover, fixed-cell analysis showed high frequencies of merotelically attached lagging chromosomes in bipolar anaphase CIN cells, and higher frequencies of merotelic attachments in multipolar vs. bipolar prometaphases. Finally, we found that multipolar CIN prometaphases typically possessed gamma-tubulin at all spindle poles, and that a significant fraction of bipolar metaphase/early anaphase CIN cells possessed more than one centrosome at a single spindle pole. Taken together, our data suggest a model by which merotelic kinetochore attachments can easily be established in multipolar prometaphases. Most of these multipolar prometaphase cells would then bi-polarize before anaphase onset, and the residual merotelic attachments would produce chromosome mis-segregation due to anaphase lagging chromosomes. We propose this spindle pole coalescence mechanism as a major contributor to chromosome instability in cancer cells.

  16. Chromosome

    Science.gov (United States)

    Chromosomes are structures found in the center (nucleus) of cells that carry long pieces of DNA. DNA ... is the building block of the human body. Chromosomes also contain proteins that help DNA exist in ...

  17. When the genome plays dice: circumvention of the spindle assembly checkpoint and near-random chromosome segregation in multipolar cancer cell mitoses.

    Directory of Open Access Journals (Sweden)

    David Gisselsson

    Full Text Available BACKGROUND: Normal cell division is coordinated by a bipolar mitotic spindle, ensuring symmetrical segregation of chromosomes. Cancer cells, however, occasionally divide into three or more directions. Such multipolar mitoses have been proposed to generate genetic diversity and thereby contribute to clonal evolution. However, this notion has been little validated experimentally. PRINCIPAL FINDINGS: Chromosome segregation and DNA content in daughter cells from multipolar mitoses were assessed by multiphoton cross sectioning and fluorescence in situ hybridization in cancer cells and non-neoplastic transformed cells. The DNA distribution resulting from multipolar cell division was found to be highly variable, with frequent nullisomies in the daughter cells. Time-lapse imaging of H2B/GFP-labelled multipolar mitoses revealed that the time from the initiation of metaphase to the beginning of anaphase was prolonged and that the metaphase plates often switched polarity several times before metaphase-anaphase transition. The multipolar metaphase-anaphase transition was accompanied by a normal reduction of cellular cyclin B levels, but typically occurred before completion of the normal separase activity cycle. Centromeric AURKB and MAD2 foci were observed frequently to remain on the centromeres of multipolar ana-telophase chromosomes, indicating that multipolar mitoses were able to circumvent the spindle assembly checkpoint with some sister chromatids remaining unseparated after anaphase. Accordingly, scoring the distribution of individual chromosomes in multipolar daughter nuclei revealed a high frequency of nondisjunction events, resulting in a near-binomial allotment of sister chromatids to the daughter cells. CONCLUSION: The capability of multipolar mitoses to circumvent the spindle assembly checkpoint system typically results in a near-random distribution of chromosomes to daughter cells. Spindle multipolarity could thus be a highly efficient

  18. MreBCD-associated Cytoskeleton is Required for Proper Segregation of the Chromosomal Terminus during the Division Cycle of Escherichia Coli

    Institute of Scientific and Technical Information of China (English)

    Yu-Jia Huo; Ling Qiao; Xiao-Wei Zheng; Cheng Cui; Yuan-Fang Ma; Feng Lu

    2015-01-01

    Background:In prokaryotic organisms,the mechanism responsible for the accurate partition of newly replicated chromosomes into daughter cells is incompletely understood.Segregation of the replication terminus of the circular prokaryotic chromosome poses special problems that have not previously been addressed.The aim of this study was to investigate the roles of several protein components (MreB,MreC,and MreD) of the prokaryotic cytoskeleton for the faithful transmission of the chromosomal terminus into daughter cells.Methods:Strain LQ1 (mreB::cat),LQ2 (mreC::cat),and LQ3 (mreD::cat) were constructed using the Red recombination system.LQ11/pLAU53,LQ12/pLAU53,LQ13/pLAU53,LQ14/pLAU53,and LQ15/pLAU53 strains were generated by Pltransduction of (tetO)240-Gm and (lacO)240-Km cassettes from strains IL2 and IL29.Fluorescence microscopy was performed to observe localization pattern of fluorescently-labeled origin and terminus foci in wild-type and mutant cells.SOS induction was monitored as gfp fluorescence from PsulA-gfp in log phase cells grown in Luria-Bertani medium at 37℃ by measurement of emission at 525 nm with excitation at 470 nm in a microplate fluorescence reader.Results:Mutational deletion of the mreB,mreC,or mreD genes was associated with selective loss of the terminus region in approximately 40% of the cells within growing cultures.This was accompanied by significant induction of the SOS DNA damage response,suggesting that deletion of terminus sequences may have occurred by chromosomal cleavage,presumably caused by ingrowth of the division septum prior to segregation of the replicated terminal.Conclusions:These results imply a role for the MreBCD cytoskeleton in the resolution of the final products of terminus replication and/ or in the specific movement of newly replicated termini away from midcell prior to completion of septal ingrowth.This would identify a previously unrecognized stage in the overall process of chromosome segregation.

  19. Caenorhabditis elegans cyclin B3 is required for multiple mitotic processes including alleviation of a spindle checkpoint-dependent block in anaphase chromosome segregation.

    Directory of Open Access Journals (Sweden)

    Gary M R Deyter

    2010-11-01

    Full Text Available The master regulators of the cell cycle are cyclin-dependent kinases (Cdks, which influence the function of a myriad of proteins via phosphorylation. Mitotic Cdk1 is activated by A-type, as well as B1- and B2-type, cyclins. However, the role of a third, conserved cyclin B family member, cyclin B3, is less well defined. Here, we show that Caenorhabditis elegans CYB-3 has essential and distinct functions from cyclin B1 and B2 in the early embryo. CYB-3 is required for the timely execution of a number of cell cycle events including completion of the MII meiotic division of the oocyte nucleus, pronuclear migration, centrosome maturation, mitotic chromosome condensation and congression, and, most strikingly, progression through the metaphase-to-anaphase transition. Our experiments reveal that the extended metaphase delay in CYB-3-depleted embryos is dependent on an intact spindle assembly checkpoint (SAC and results in salient defects in the architecture of holocentric metaphase chromosomes. Furthermore, genetically increasing or decreasing dynein activity results in the respective suppression or enhancement of CYB-3-dependent defects in cell cycle progression. Altogether, these data reveal that CYB-3 plays a unique, essential role in the cell cycle including promoting mitotic dynein functionality and alleviation of a SAC-dependent block in anaphase chromosome segregation.

  20. Mapping the Flavor Contributing Traits on "Fengwei Melon" (Cucumis melo L. Chromosomes Using Parent Resequencing and Super Bulked-Segregant Analysis.

    Directory of Open Access Journals (Sweden)

    Hong Zhang

    Full Text Available We used a next-generation high-throughput sequencing platform to resequence the Xinguowei and Shouxing melon cultivars, the parents of Fengwei melon. We found 84% of the reads (under a coverage rate of "13×" placed on the reference genome DHL92. There were 2,550,000 single-nucleotide polymorphisms and 140,000 structural variations in the two genomes. We also identified 1,290 polymorphic genes between Xinguowei and Shouxing. We combined specific length amplified fragment sequencing (SLAF-seq and bulked-segregant analysis (super-BSA to analyze the two parents and the F2 extreme phenotypes. This combined method yielded 12,438,270 reads, 46,087 SLAF tags, and 4,480 polymorphic markers (average depth of 161.81×. There were six sweet trait-related regions containing 13 differential SLAF markers, and 23 sour trait-related regions containing 48 differential SLAF markers. We further fine-mapped the sweet trait to the genomic regions on chromosomes 6, 10, 11, and 12. Correspondingly, we mapped the sour trait-related genomic regions to chromosomes 2, 3, 4, 5, 9, and 12. Finally, we positioned nine of the 61 differential markers in the sweet and sour trait candidate regions on the parental genome. These markers corresponded to one sweet and eight sour trait-related genes. Our study provides a basis for marker-assisted breeding of desirable sweet and sour traits in Fengwei melons.

  1. Mapping the Flavor Contributing Traits on "Fengwei Melon" (Cucumis melo L.) Chromosomes Using Parent Resequencing and Super Bulked-Segregant Analysis.

    Science.gov (United States)

    Zhang, Hong; Yi, Hongping; Wu, Mingzhu; Zhang, Yongbin; Zhang, Xuejin; Li, Meihua; Wang, Guangzhi

    2016-01-01

    We used a next-generation high-throughput sequencing platform to resequence the Xinguowei and Shouxing melon cultivars, the parents of Fengwei melon. We found 84% of the reads (under a coverage rate of "13×") placed on the reference genome DHL92. There were 2,550,000 single-nucleotide polymorphisms and 140,000 structural variations in the two genomes. We also identified 1,290 polymorphic genes between Xinguowei and Shouxing. We combined specific length amplified fragment sequencing (SLAF-seq) and bulked-segregant analysis (super-BSA) to analyze the two parents and the F2 extreme phenotypes. This combined method yielded 12,438,270 reads, 46,087 SLAF tags, and 4,480 polymorphic markers (average depth of 161.81×). There were six sweet trait-related regions containing 13 differential SLAF markers, and 23 sour trait-related regions containing 48 differential SLAF markers. We further fine-mapped the sweet trait to the genomic regions on chromosomes 6, 10, 11, and 12. Correspondingly, we mapped the sour trait-related genomic regions to chromosomes 2, 3, 4, 5, 9, and 12. Finally, we positioned nine of the 61 differential markers in the sweet and sour trait candidate regions on the parental genome. These markers corresponded to one sweet and eight sour trait-related genes. Our study provides a basis for marker-assisted breeding of desirable sweet and sour traits in Fengwei melons.

  2. Mutation of histone H3 serine 86 disrupts GATA factor Ams2 expression and precise chromosome segregation in fission yeast

    OpenAIRE

    Kim Kiat Lim; Terenze Yao Rui Ong; Yue Rong Tan; Eugene Guorong Yang; Bingbing Ren; Kwi Shan Seah; Zhe Yang; Tsu Soo Tan; Dymock, Brian W.; Ee Sin Chen

    2015-01-01

    Eukaryotic genomes are packed into discrete units, referred to as nucleosomes, by organizing around scaffolding histone proteins. The interplay between these histones and the DNA can dynamically regulate the function of the chromosomal domain. Here, we interrogated the function of a pair of juxtaposing serine residues (S86 and S87) that reside within the histone fold of histone H3. We show that fission yeast cells expressing a mutant histone H3 disrupted at S86 and S87 (hht2-S86AS87A) exhibit...

  3. Mutations reducing replication from R-loops suppress the defects of growth, chromosome segregation and DNA supercoiling in cells lacking topoisomerase I and RNase HI activity.

    Science.gov (United States)

    Usongo, Valentine; Martel, Makisha; Balleydier, Aurélien; Drolet, Marc

    2016-04-01

    R-loop formation occurs when the nascent RNA hybridizes with the template DNA strand behind the RNA polymerase. R-loops affect a wide range of cellular processes and their use as origins of replication was the first function attributed to them. In Escherichia coli, R-loop formation is promoted by the ATP-dependent negative supercoiling activity of gyrase (gyrA and gyrB) and is inhibited by topoisomerase (topo) I (topA) relaxing transcription-induced negative supercoiling. RNase HI (rnhA) degrades the RNA moiety of R-loops. The depletion of RNase HI activity in topA null mutants was previously shown to lead to extensive DNA relaxation, due to DNA gyrase inhibition, and to severe growth and chromosome segregation defects that were partially corrected by overproducing topo III (topB). Here, DNA gyrase assays in crude cell extracts showed that the ATP-dependent activity (supercoiling) of gyrase but not its ATP-independent activity (relaxation) was inhibited in topA null cells lacking RNase HI. To characterize the cellular event(s) triggered by the absence of RNase HI, we performed a genetic screen for suppressors of the growth defect of topA rnhA null cells. Suppressors affecting genes in replication (holC2::aph and dnaT18::aph) nucleotide metabolism (dcd49::aph), RNA degradation (rne59::aph) and fimbriae synthesis (fimD22::aph) were found to reduce replication from R-loops and to restore supercoiling, thus pointing to a correlation between R-loop-dependent replication in topA rnhA mutants and the inhibition of gyrase activity and growth. Interestingly, the position of fimD on the E. coli chromosome corresponds to the site of one of the five main putative origins of replication from R-loops in rnhA null cells recently identified by next-generation sequencing, thus suggesting that the fimD22::aph mutation inactivated one of these origins. Furthermore, we show that topo III overproduction is unable to complement the growth defect of topA rnhA null mutants at low

  4. Chromosome Segregation: Disarming the Protector

    OpenAIRE

    Sanyal, Swastika; Kovacikova, Ines; Gregan, Juraj

    2013-01-01

    Summary One of the key features of meiosis is that shugoshin in complex with protein phosphatase 2A (PP2A) protects centromeric cohesin during meiosis I, but not during meiosis II. A new model suggests that a PP2A inhibitor mediates deprotection of centromeric cohesin during meiosis II.

  5. Quantitative Proteomics Reveals That the Inhibition of Na(+)/K(+)-ATPase Activity Affects S-Phase Progression Leading to a Chromosome Segregation Disorder by Attenuating the Aurora A Function in Hepatocellular Carcinoma Cells.

    Science.gov (United States)

    Xu, Zhongwei; Wang, Fengmei; Fan, Fengxu; Gu, Yanjun; Shan, Nana; Meng, Xiangyan; Cheng, Shixiang; Liu, Yingfu; Wang, Chengyan; Song, Yueying; Xu, Ruicheng

    2015-11-01

    Many studies have shown the Na(+)/K(+)-ATPase (NKA) might be a potential target for anticancer therapy. Cardiac glycosides (CGs), as a family of naturally compounds, inhibited the NKA activity. The present study investigates the antitumor effect of ouabain and elucidates the pharmacological mechanisms of CG activity in liver cancer HepG2 cell using SILAC coupled to LC-MS/MS method. Bioinformatics analysis of 330 proteins that were changed in cells under treatment with 0.5 μmol/L ouabain showed that the biological processes are associated with an acute inflammatory response, cell cycle, oxidation reduction, chromosome segregation, and DNA metabolism. We confirmed that ouabain induced chromosome segregation disorder and S-cell cycle block by decreasing the expression of AURKA, SMC2, Cyclin D, and p-CDK1 as well as increasing the expression of p53. We found that the overexpression or inhibition of AURKA significantly reduced or enhanced the ouabain-mediated the anticancer effects. Our findings suggest that AURKA is involved in the anticancer mechanisms of ouabain in HepG2 cells. PMID:26491887

  6. Measuring Segregation

    OpenAIRE

    David M. Frankel; Oscar Volij

    2004-01-01

    We propose a set of axioms for the measurement of multigroup school segregation. They are motivated by two criteria: do ethnic groups have similar distributions across schools? And are schools ethnically representative of their district? Our axioms are satisfied by a unique ordering. It is represented by the Mutual Information index. This index, originally proposed by Henri Theil, has a more intuitive decomposition than other indices. As an application, we find that segregation between distri...

  7. A dynamic meiotic SUN belt includes the zygotene-stage telomere bouquet and is disrupted in chromosome segregation mutants of maize (Zea mays L..

    Directory of Open Access Journals (Sweden)

    Shaun Patrick Murphy

    2014-07-01

    Full Text Available The nuclear envelope (NE plays an essential role in meiotic telomere behavior and links the cytoplasm and nucleoplasm during homologous chromosome pairing and recombination in many eukaryotic species. Resident NE proteins including SUN (Sad-1/UNC-84 and KASH (Klarsicht/ANC-1/Syne-homology domain proteins are known to interact forming the Linker of Nucleoskeleton and Cytoskeleton (LINC complex that connects chromatin to the cytoskeleton. To investigate the possible cross-kingdom conservation of SUN protein functions in plant meiosis, we immunolocalized maize SUN2 using 3D microscopy of pollen mother cells from maize (Zea mays L., a large-genome plant model with a canonical NE zygotene-stage telomere bouquet. We detected SUN2 at the nuclear periphery and found that it exhibited a distinct belt-like structure that transitioned to a half-belt during the zygotene stage and back to a full belt during and beyond the pachytene stage. The zygotene-stage half-belt SUN structure was shown by 3D immuno-FISH to include the NE-associated telomere cluster that defines the bouquet stage and coincides with homologous chromosome synapsis. Microtubule and filamentous actin staining patterns did not show any obvious belt or a retracted-like structure other than a general enrichment of tubulin staining distributed widely around the nucleus and throughout the cytoplasm. Genetic disruption of the meiotic SUN belt staining patterns with three different meiosis-specific mutants, desynaptic (dy1, asynaptic1 (as1, and divergent spindle1 (dv1 provides additional evidence for the role of the nuclear envelope in meiotic chromosome behavior. Taking into account all of the observations from this study, we propose that the maize SUN belt is directly or indirectly involved in meiotic telomere dynamics, chromosome synapsis, and possibly integration of signals and forces across the meiotic prophase nuclear envelope.

  8. Waste segregation

    International Nuclear Information System (INIS)

    A scoping study has been undertaken to determine the state-of-the-art of waste segregation technology as applied to the management of low-level waste (LLW). Present-day waste segregation practices were surveyed through a review of the recent literature and by means of personal interviews with personnel at selected facilities. Among the nuclear establishments surveyed were Department of Energy (DOE) laboratories and plants, nuclear fuel cycle plants, public and private laboratories, institutions, industrial plants, and DOE and commercially operated shallow land burial sites. These survey data were used to analyze the relationship between waste segregation practices and waste treatment/disposal processes, to assess the developmental needs for improved segregation technology, and to evaluate the costs and benefits associated with the implementation of waste segregation controls. This task was planned for completion in FY 1981. It should be noted that LLW management practices are now undergoing rapid change such that the technology and requirements for waste segregation in the near future may differ significantly from those of the present day. 8 figures

  9. Sgo1 is required for co-segregation of sister chromatids during achiasmate meiosis I

    OpenAIRE

    Dudas, Andrej; Ahmad, Shazia; Gregan, Juraj

    2011-01-01

    The reduction of chromosome number during meiosis is achieved by two successive rounds of chromosome segregation, called meiosis I and meiosis II. While meiosis II is similar to mitosis in that sister kinetochores are bi-oriented and segregate to opposite poles, recombined homologous chromosomes segregate during the first meiotic division. Formation of chiasmata, mono-orientation of sister kinetochores and protection of centromeric cohesion are three major features of meiosis I chromosomes wh...

  10. School Segregation, Residential Segregation: Some Speculation.

    Science.gov (United States)

    Kantrowitz, Nathan

    This essay addressed the question of to what extent does school segregation and school desegregation policy shape residential segregation. Census data, ethnic segregation, voluntary self-segregation, and attitude surveys are discussed in the residential segregation section. The Wolf and Lebeaux study is critically appraised in reference to school…

  11. Residentielle Segregation

    OpenAIRE

    Dangschat, Jens S.

    2014-01-01

    "Die residentielle Segregation - verstanden als die ungleichmäßige Verteilung der Wohngelegenheiten sozialer Gruppen - wird über Segregationsindices als relative Abweichung der Anteilswerte in städtischen Teilgebieten gegenüber der Gesamtstadt gemessen. Diese Durchschnittswerte sagen jedoch nichts darüber aus, ob es in einer städtischen Agglomeration 'problematische' sozialräumliche Konstellationen gibt, sie haben daher keinen kommunalpolitischen oder stadtentwicklungsplanerischen Wert. Zudem...

  12. Micromechanics of human mitotic chromosomes

    International Nuclear Information System (INIS)

    Eukaryote cells dramatically reorganize their long chromosomal DNAs to facilitate their physical segregation during mitosis. The internal organization of folded mitotic chromosomes remains a basic mystery of cell biology; its understanding would likely shed light on how chromosomes are separated from one another as well as into chromosome structure between cell divisions. We report biophysical experiments on single mitotic chromosomes from human cells, where we combine micromanipulation, nano-Newton-scale force measurement and biochemical treatments to study chromosome connectivity and topology. Results are in accord with previous experiments on amphibian chromosomes and support the 'chromatin network' model of mitotic chromosome structure. Prospects for studies of chromosome-organizing proteins using siRNA expression knockdowns, as well as for differential studies of chromosomes with and without mutations associated with genetic diseases, are also discussed

  13. Meiosis I: When Chromosomes Undergo Extreme Makeover

    OpenAIRE

    Miller, Matthew P.; Amon, Angelika; Ünal, Elçin

    2013-01-01

    The ultimate success of cell division relies on the accurate partitioning of the genetic material. Errors in this process occur in nearly all tumors and are the leading cause of miscarriages and congenital birth defects in humans. Two cell divisions, mitosis and meiosis, use common as well as unique mechanisms to ensure faithful chromosome segregation. In mitosis, alternating rounds of DNA replication and chromosome segregation preserves the chromosome complement of the progenitor cell. In co...

  14. Segregation of Polymers in Confined Spaces

    CERN Document Server

    Liu, Ya

    2009-01-01

    We investigate the motion of two overlapping polymers with self-avoidance confined in a narrow 2d box. A statistical model is constructed using blob free-energy arguments. We find spontaneous segregation under the condition: $L > R_{//}$, and mixing under $L < R_{//}$, where L is the length of the box, and $R_{//}$ the polymer extension in an infinite slit. Segregation time scales are determined by solving a mean first-passage time problem, and by performing Monte Carlo simulations. Predictions of the two methods show good agreement. Our results may elucidate a driving force for chromosomes segregation in bacteria.

  15. Radiation effects on segregating seed in rice

    International Nuclear Information System (INIS)

    Seeds of segregating lines selected from dES treated M2 populations of rice were irradiated with gamma rays with a view to enhance the variabiity and thus selection parameter. Seedling and mature plant parameters and frequency of dividing cells showed reduction upon treatment. Very high frequency of chromosomal interchanges including rare cases of those involving the two nucleolar chromosomes and plants with 13 II were recorded. Several types of desirable morphological mutants were isolated. 7 refs., 3 tables. (author)

  16. An EM algorithm for mapping segregation distortion loci

    OpenAIRE

    Zhang Yuan-Ming; Zhu Chengsong

    2007-01-01

    Abstract Background Chromosomal region that causes distorted segregation ratios is referred to as segregation distortion locus (SDL). The distortion is caused either by differential representation of SDL genotypes in gametes before fertilization or by viability differences of SDL genotypes after fertilization but before genotype scoring. In both cases, observable phenotypes are distorted for marker loci in the chromosomal region close to the SDL. Under the quantitative genetics model for viab...

  17. Expression of homosapiens chromosome segregation gene in homogenous nasopharyngeal carcinoma tissue cells%染色体分离基因在纯化鼻咽癌组织中的表达

    Institute of Scientific and Technical Information of China (English)

    刘仲奇; 田勇泉; 刘俊秀; 张迎宏; 马芙蓉; 胡永芳

    2007-01-01

    目的 研究染色体分离基因(homosapiens chromosome segregation gene,CSE1L)在纯化鼻咽癌及非癌组织中的表达.方法 首先从全基因组表达谱中筛选到鼻咽癌候选癌基因CSE1L.结合RNA保护、显微切割及线性扩增技术,获得纯化鼻咽组织中反义RNA(antisense RNA,aRNA),采用半定量逆转录聚合酶链式反应(semi-quantitative reverse transcriptionpolymerase chain reaction,sqRT-PCR)研究从全基因组表达谱中筛选的候选癌基因-CSE1L在两种不同纯化鼻咽组织aRNA中的表达.结果 在纯化鼻咽癌组织和鼻咽部非癌组织全基因组表达谱中,CSE1L基因表达值分别为1.056±0.296和0.465±0.835,相差2.27倍,两组比较有显著性差异(df=16,t=4.317,P=0.001<0.01).sqRT-PCR检测纯化鼻咽癌组织及非癌组织aRNA中CSE1L基因的表达,分别为1.740±1.105和0.618±0.183,两组比较有显著性差异(df=30,t=3.159,P=0.004<0.01).结论 利用全基因组芯片构建基因表达谱可筛选到鼻咽癌发病相关的候选靶基因,sqRT-PCR可验证芯片杂交结果,CSE1L基因是鼻咽癌发生、发展过程中重要的候选癌基因.

  18. Overcoming Triple Segregation

    Science.gov (United States)

    Gandara, Patricia

    2010-01-01

    Latinos are, after whites, the most segregated student group in the United States, and their segregation is closely tied to poor academic outcomes. Latinos experience a triple segregation: by race/ethnicity, poverty, and language. Racial segregation perpetuates negative stereotypes, reduces the likelihood of a strong teaching staff, and is often…

  19. Surface Segregation in YSZ

    DEFF Research Database (Denmark)

    Bay, Lasse; Zachau-Christiansen, Birgit; Jacobsen, Torben

    1998-01-01

    The space charge layer formed due to segregation of yttria and oxygen ion vacancies in YSZ is described by a simple model. Effects of impurities segregation are omitted.......The space charge layer formed due to segregation of yttria and oxygen ion vacancies in YSZ is described by a simple model. Effects of impurities segregation are omitted....

  20. Poisson Indices of Segregation

    OpenAIRE

    Angelo, Mele

    2009-01-01

    Existing indices of residential segregation are based on an arbitrary partition of the city in neighborhoods: given a spatial distribution of racial groups, the index provides different levels of segregation for different partitions. This paper proposes a method in which individual locations are mapped to aggregate levels of segregation, avoiding arbitrary partitions. Assuming a simple spatial process driving the locations of different racial groups, I define a location-specific segregation i...

  1. Nonmetropolitan Residential Segregation Revisited.

    Science.gov (United States)

    Murdock, Steve H.; And Others

    1994-01-01

    Analysis of 1980 and 1990 Censuses of Population and Housing for Texas found overall black-white and Anglo-Hispanic residential segregation declined substantially. Nonmetropolitan counties were more segregated than metropolitan counties in both years, but growing nonmetro places showed the greatest segregation declines. Analyses controlling for…

  2. Condensin-Based Chromosome Organization from Bacteria to Vertebrates.

    Science.gov (United States)

    Hirano, Tatsuya

    2016-02-25

    Condensins are large protein complexes that play a central role in chromosome organization and segregation in the three domains of life. They display highly characteristic, rod-shaped structures with SMC (structural maintenance of chromosomes) ATPases as their core subunits and organize large-scale chromosome structure through active mechanisms. Most eukaryotic species have two distinct condensin complexes whose balanced usage is adapted flexibly to different organisms and cell types. Studies of bacterial condensins provide deep insights into the fundamental mechanisms of chromosome segregation. This Review surveys both conserved features and rich variations of condensin-based chromosome organization and discusses their evolutionary implications.

  3. Polymer segregation under confinement: Influences of macromolecular crowding and the interaction between the polymer and crowders

    Science.gov (United States)

    Chen, Yuhao; Yu, Wancheng; Wang, Jiajun; Luo, Kaifu

    2015-10-01

    Entropy driven polymer segregation in confinements as a model for chromosome separation in bacteria has attracted wide attention; however, the effects of macromolecular crowding and the interaction between the binding protein and the newly replicated DNA on the segregation dynamics are not clear. Using Langevin dynamics simulations, we investigate the influences of crowders and the attractive interaction between the polymer and a small number of crowders on segregation of two overlapping polymers under a cylindrical confinement. We find that the segregation time increases with increasing the volume fraction of crowders due to the slower chain diffusion in crowded environments. For a fixed volume fraction of crowders, the segregation time decreases with increasing the size of crowders. Moreover, the attractive interaction between the polymer and a small number of crowders can significantly facilitate the chain segregation. These results are important for understanding the chromosome segregation in living cells.

  4. GSK-3 inhibitors induce chromosome instability

    Directory of Open Access Journals (Sweden)

    Staples Oliver D

    2007-08-01

    Full Text Available Abstract Background Several mechanisms operate during mitosis to ensure accurate chromosome segregation. However, during tumour evolution these mechanisms go awry resulting in chromosome instability. While several lines of evidence suggest that mutations in adenomatous polyposis coli (APC may promote chromosome instability, at least in colon cancer, the underlying mechanisms remain unclear. Here, we turn our attention to GSK-3 – a protein kinase, which in concert with APC, targets β-catenin for proteolysis – and ask whether GSK-3 is required for accurate chromosome segregation. Results To probe the role of GSK-3 in mitosis, we inhibited GSK-3 kinase activity in cells using a panel of small molecule inhibitors, including SB-415286, AR-A014418, 1-Azakenpaullone and CHIR99021. Analysis of synchronised HeLa cells shows that GSK-3 inhibitors do not prevent G1/S progression or cell division. They do, however, significantly delay mitotic exit, largely because inhibitor-treated cells have difficulty aligning all their chromosomes. Although bipolar spindles form and the majority of chromosomes biorient, one or more chromosomes often remain mono-oriented near the spindle poles. Despite a prolonged mitotic delay, anaphase frequently initiates without the last chromosome aligning, resulting in chromosome non-disjunction. To rule out the possibility of "off-target" effects, we also used RNA interference to selectively repress GSK-3β. Cells deficient for GSK-3β exhibit a similar chromosome alignment defect, with chromosomes clustered near the spindle poles. GSK-3β repression also results in cells accumulating micronuclei, a hallmark of chromosome missegregation. Conclusion Thus, not only do our observations indicate a role for GSK-3 in accurate chromosome segregation, but they also raise the possibility that, if used as therapeutic agents, GSK-3 inhibitors may induce unwanted side effects by inducing chromosome instability.

  5. Local versus overall segregation measures

    OpenAIRE

    Olga Alonso-Villar; Coral del Río

    2008-01-01

    This paper proposes a framework in which to study the segregation of a target group in a multigroup context, according either to an evenness perception or to a representativeness view of segregation, and offers a bridge between local segregation and overall segregation. In doing so, this paper first presents an axiomatic set-up within which local segregation measures can be evaluated, and defines local segregation curves. Next, a class of additive segregation indexes, related to the generaliz...

  6. On the Measurement of Segregation

    OpenAIRE

    Federico Echenique; Roland G. Fryer, Jr.

    2005-01-01

    This paper develops a measure of segregation based on two premises: (1) a measure of segregation should disaggregate to the level of individuals, and (2) an individual is more segregated the more segregated are the agents with whom she interacts. Developing three desirable axioms that any segregation measure should satisfy, we prove that one and only one segregation index satisfies our three axioms, and the two aims mentioned above; which we coin the Spectral Segregation Index. We apply the i...

  7. Measuring School Segregation

    OpenAIRE

    David M. Frankel; Volij, Oscar

    2011-01-01

    Using only ordinal axioms, we characterize several multi-group school segregation indices: the Atkinson Indices for the class of school districts with a given fixed number of ethnic groups and the Mutual Information Index for the class of all districts. Properties of other school segregation indices are also discussed. In an empirical application, we document a weakening of the effect of ethnicity on school assignment from 1987/8 to 2007/8. We also show that segregation between districts with...

  8. SYNAPTONEMAL COMPLEX ANALYSIS OF MUTAGEN EFFECTS ON MEIOTIC CHROMOSOME STRUCTURE AND BEHAVIOR

    Science.gov (United States)

    Homologous chromosome synapsis and crossing-over at meiosis are basic to mammalian gamete development. hey achieve genetic recombination, regulate chromosome segregation, and are believed to function in repair and maturation. ynaptonemal complexes (SCs) are axial correlates of me...

  9. Segregation and Civic Virtue

    Science.gov (United States)

    Merry, Michael S.

    2012-01-01

    In this essay Michael Merry defends the following prima facie argument: that civic virtue is not dependent on integration and in fact may be best fostered under conditions of segregation. He demonstrates that civic virtue can and does take place under conditions of involuntary segregation, but that voluntary separation--as a response to…

  10. Neighborhood Schools and Racial Segregation

    Science.gov (United States)

    Kelleher, Daniel T.

    1975-01-01

    Neighborhood school concept and racially segregated residential patterns account for most of the segregation in American public schools today. The focus of this article will be to explain the reasons for residential segregation. (Author/RK)

  11. Stable persistence of the yeast plasmid by hitchhiking on chromosomes during vegetative and germ-line divisions of host cells

    OpenAIRE

    Sau, Soumitra; Liu, Yen-Ting; Ma, Chien-Hui; Jayaram, Makkuni

    2015-01-01

    The chromosome-like stability of the Saccharomyces cerevisiae plasmid 2 micron circle likely stems from its ability to tether to chromosomes and segregate by a hitchhiking mechanism. The plasmid partitioning system, responsible for chromosome-coupled segregation, is comprised of 2 plasmid coded proteins Rep1 and Rep2 and a partitioning locus STB. The evidence for the hitchhiking model for mitotic plasmid segregation, although compelling, is almost entirely circumstantial. Direct tests for pla...

  12. Microtubule detyrosination guides chromosomes during mitosis

    OpenAIRE

    Barisic, Marin; Silva e Sousa, Ricardo; Tripathy, Suvranta K.; Magiera, Maria M.; Zaytsev, Anatoly V.; Pereira, Ana L.; Janke, Carsten; Grishchuk, Ekaterina L.; Maiato, Helder

    2015-01-01

    Before chromosomes segregate into daughter cells they align at the mitotic spindle equator, a process known as chromosome congression. CENP-E/Kinesin-7 is a microtubule plus-end-directed kinetochore motor required for congression of pole-proximal chromosomes. Because the plus-ends of many astral microtubules in the spindle point to the cell cortex, it remains unknown how CENP-E guides pole-proximal chromosomes specifically towards the equator. Here we found that congression of pole-proximal c...

  13. Mitosis. Microtubule detyrosination guides chromosomes during mitosis.

    Science.gov (United States)

    Barisic, Marin; Silva e Sousa, Ricardo; Tripathy, Suvranta K; Magiera, Maria M; Zaytsev, Anatoly V; Pereira, Ana L; Janke, Carsten; Grishchuk, Ekaterina L; Maiato, Helder

    2015-05-15

    Before chromosomes segregate into daughter cells, they align at the mitotic spindle equator, a process known as chromosome congression. Centromere-associated protein E (CENP-E)/Kinesin-7 is a microtubule plus-end-directed kinetochore motor required for congression of pole-proximal chromosomes. Because the plus-ends of many astral microtubules in the spindle point to the cell cortex, it remains unknown how CENP-E guides pole-proximal chromosomes specifically toward the equator. We found that congression of pole-proximal chromosomes depended on specific posttranslational detyrosination of spindle microtubules that point to the equator. In vitro reconstitution experiments demonstrated that CENP-E-dependent transport was strongly enhanced on detyrosinated microtubules. Blocking tubulin tyrosination in cells caused ubiquitous detyrosination of spindle microtubules, and CENP-E transported chromosomes away from spindle poles in random directions. Thus, CENP-E-driven chromosome congression is guided by microtubule detyrosination. PMID:25908662

  14. Plasmid segregation mechanisms

    DEFF Research Database (Denmark)

    Ebersbach, Gitte; Gerdes, Kenn; Charbon, Gitte Ebersbach

    2005-01-01

    Bacterial plasmids encode partitioning (par) loci that ensure ordered plasmid segregation prior to cell division. par loci come in two types: those that encode actin-like ATPases and those that encode deviant Walker-type ATPases. ParM, the actin-like ATPase of plasmid R1, forms dynamic filaments...... that segregate plasmids paired at mid-cell to daughter cells. Like microtubules, ParM filaments exhibit dynamic instability (i.e., catastrophic decay) whose regulation is an important component of the DNA segregation process. The Walker box ParA ATPases are related to MinD and form highly dynamic, oscillating...... filaments that are required for the subcellular movement and positioning of plasmids. The role of the observed ATPase oscillation is not yet understood. However, we propose a simple model that couples plasmid segregation to ParA oscillation. The model is consistent with the observed movement...

  15. Predicting polydisperse granular segregation

    OpenAIRE

    Isner, Austin; Schlick, Conor P.; Umbanhowar, Paul B.; Ottino, Julio M.; Lueptow, Richard M.

    2014-01-01

    Most granular materials in industrial applications and natural settings are size-polydisperse, but most models and simulations of segregation consider only bidisperse particle distributions. Here, we extend our recently developed theoretical advection–diffusion–segregation model to polydisperse particle distributions. To test the theoretical approach, we model and simulate grains log-normally distributed by size in a chute flow. In steady state, material near the free surface is dominated by ...

  16. Segregation by friction

    OpenAIRE

    Kondic, L.; Hartley, R. R.; Tennakoon, S. G. K.; Painter, B; Behringer, R. P.

    2002-01-01

    Granular materials are known to separate by size under a variety of circumstances. Experiments presented here and elucidated by modeling and MD simulation document a new segregation mechanism, namely segregation by friction. The experiments are carried out by placing steel spheres on a horizontal plane enclosed by rectangular sidewalls, and subjecting them to horizontal shaking. Half the spheres are highly smooth; the remainder are identical to the first half, except that their surfaces have ...

  17. Homologue pairing, recombination and segregation in Caenorhabditis elegans.

    Science.gov (United States)

    Zetka, M

    2009-01-01

    Meiosis in the free-living, hermaphroditic nematode Caenorhabditis elegans is marked by the same highly conserved features observed in other sexually reproducing systems. Accurate chromosome segregation at the meiotic divisions depends on earlier landmark events of meiotic prophase, including the pairing of homologous chromosomes, synapsis between them, and the formation of crossovers. Dissection of these processes has revealed a unique simplification of meiotic mechanisms that impact the interpretation of meiotic chromosome behaviour in more complex systems. Chromosome sites required for chromosome pairing are consolidated to one end of each chromosome, the many sites of recombination initiation are resolved into a single crossover for each chromosome pair, and the diffuse (holocentric) kinetic activity that extends along the length of the mitotic chromosomes is reduced to a single end of each meiotic chromosome. Consequently, studies from the nematode have illuminated and challenged long-standing concepts of homologue pairing mechanisms, crossover interference, and kinetochore structure. Because chromosome pairing, synapsis, and recombination can proceed independently of one another, C. elegans has provided a simplified system for studying these processes and the mechanisms mediating their coordination during meiosis. This review covers the major features of C. elegans meiosis with emphasis on its contributions to understanding essential meiotic processes. PMID:18948706

  18. Estimating tempo and mode of Y chromosome turnover: explaining Y chromosome loss with the fragile Y hypothesis.

    Science.gov (United States)

    Blackmon, Heath; Demuth, Jeffery P

    2014-06-01

    Chromosomal sex determination is phylogenetically widespread, having arisen independently in many lineages. Decades of theoretical work provide predictions about sex chromosome differentiation that are well supported by observations in both XY and ZW systems. However, the phylogenetic scope of previous work gives us a limited understanding of the pace of sex chromosome gain and loss and why Y or W chromosomes are more often lost in some lineages than others, creating XO or ZO systems. To gain phylogenetic breadth we therefore assembled a database of 4724 beetle species' karyotypes and found substantial variation in sex chromosome systems. We used the data to estimate rates of Y chromosome gain and loss across a phylogeny of 1126 taxa estimated from seven genes. Contrary to our initial expectations, we find that highly degenerated Y chromosomes of many members of the suborder Polyphaga are rarely lost, and that cases of Y chromosome loss are strongly associated with chiasmatic segregation during male meiosis. We propose the "fragile Y" hypothesis, that recurrent selection to reduce recombination between the X and Y chromosome leads to the evolution of a small pseudoautosomal region (PAR), which, in taxa that require XY chiasmata for proper segregation during meiosis, increases the probability of aneuploid gamete production, with Y chromosome loss. This hypothesis predicts that taxa that evolve achiasmatic segregation during male meiosis will rarely lose the Y chromosome. We discuss data from mammals, which are consistent with our prediction. PMID:24939995

  19. Understanding Segregation Processes

    Science.gov (United States)

    Bruch, Elizabeth

    There is growing consensus that living in neighborhoods of concentrated poverty increases the likelihood of social problems such as teenage parenthood, drug and alcohol use, crime victimization, and chronic unemployment. Neighborhood inequality is also implicated in studies of enduring race/ethnic health disparities, and there are recent moves to broaden the definition of health care policy to policies targeting social inequality (Mechanic 2007). Residential segregation affects health outcomes in several different ways. First, income, education, and occupation are all strongly related to health (Adler and Newman 2002). Segregation is a key mechanism through which socioeconomic inequality is perpetuated and reinforced, as it hinders the upward mobility of disadvantaged groups by limiting their educational and employment opportunities. Second, segregation increases minority exposure to unhealthy neighborhood environments. Residential segregation creates areas with concentrated poverty and unemployment, both of which are key factors that predict violence and create racial differences in homicide (Samson and Wilson 1995). Neighborhood characteristics, such as exposure to environmental hazards, fear of violence, and access to grocery stores, affect health risks and health behaviors (Cheadle et al. 1991). Tobacco and alcohol industries also advertise their products disproportionately in poor, minority areas (Moore, Williams, and Qualls 1996). Finally, residential segregation leads to inequalitie in health care resources, which contributes to disparities in quality of treatment (Smedley, Stith, and Nelson 2002).

  20. Measuring Inequality and Segregation

    CERN Document Server

    Roberto, Elizabeth

    2015-01-01

    In this paper, I introduce the Divergence Index, a conceptually intuitive and methodologically rigorous measure of inequality and segregation. The index measures the difference between a distribution of interest and another empirical, theoretical, or normative distribution. The Divergence Index provides flexibility in specifying a theoretically meaningful basis for evaluating inequality. It evaluates how surprising an empirical distribution is given a theoretical distribution that represents equality. I demonstrate the unique features of the new measure, as well as deriving its mathematical equivalence with Theil's Inequality Index and the Information Theory Index. I compare the dynamics of the measures using simulated data, and an empirical analysis of racial residential segregation in the Detroit, MI, metro area. The Information Theory Index has become the gold standard for decomposition analyses of segregation. I show that although the Information Theory Index can be decomposed for subareas, it is misleadi...

  1. The Role of Residential Segregation in Contemporary School Segregation

    Science.gov (United States)

    Frankenberg, Erica

    2013-01-01

    Inaction to address housing segregation in metropolitan areas has resulted in persistently high levels of residential segregation. As the Supreme Court has recently limited school districts' voluntary integration efforts, this article considers the role of residential segregation in maintaining racially isolated schools, namely what is known…

  2. Applied Thermodynamics: Grain Boundary Segregation

    OpenAIRE

    Pavel Lejček; Lei Zheng; Siegfried Hofmann; Mojmír Šob

    2014-01-01

    Chemical composition of interfaces—free surfaces and grain boundaries—is generally described by the Langmuir–McLean segregation isotherm controlled by Gibbs energy of segregation. Various components of the Gibbs energy of segregation, the standard and the excess ones as well as other thermodynamic state functions—enthalpy, entropy and volume—of interfacial segregation are derived and their physical meaning is elucidated. The importance of the thermodynamic state functions of grain boundary se...

  3. Residential Segregation and School Integration.

    Science.gov (United States)

    Rivkin, Steven G.

    1994-01-01

    Asserts that school districts' efforts to integrate schools have failed to ameliorate the racial isolation of black students. Finds that schools remain segregated primarily because of continued residential segregation and that school integration efforts have had little long-term effect on residential segregation. (CFR)

  4. Analysis of the terminus region of the Caulobacter crescentus chromosome and identification of the dif site

    DEFF Research Database (Denmark)

    Jensen, Rasmus Bugge

    2006-01-01

    The terminus region of the Caulobacter crescentus chromosome and the dif chromosome dimer resolution site were characterized. The Caulobacter genome contains skewed sequences that abruptly switch strands at dif and may have roles in chromosome maintenance and segregation. Absence of dif or the Xer...

  5. Co-segregation of yeast plasmid sisters under monopolin-directed mitosis suggests association of plasmid sisters with sister chromatids

    OpenAIRE

    Liu, Yen-Ting; Ma, Chien-Hui; Jayaram, Makkuni

    2013-01-01

    The 2-micron plasmid, a high copy extrachromosomal element in Saccharomyces cerevisiae, propagates itself with nearly the same stability as the chromosomes of its host. Plasmid stability is conferred by a partitioning system consisting of the plasmid-coded proteins Rep1 and Rep2 and a cis-acting locus STB. Circumstantial evidence suggests that the partitioning system couples plasmid segregation to chromosome segregation during mitosis. However, the coupling mechanism has not been elucidated. ...

  6. Applied Thermodynamics: Grain Boundary Segregation

    Directory of Open Access Journals (Sweden)

    Pavel Lejček

    2014-03-01

    Full Text Available Chemical composition of interfaces—free surfaces and grain boundaries—is generally described by the Langmuir–McLean segregation isotherm controlled by Gibbs energy of segregation. Various components of the Gibbs energy of segregation, the standard and the excess ones as well as other thermodynamic state functions—enthalpy, entropy and volume—of interfacial segregation are derived and their physical meaning is elucidated. The importance of the thermodynamic state functions of grain boundary segregation, their dependence on volume solid solubility, mutual solute–solute interaction and pressure effect in ferrous alloys is demonstrated.

  7. Segregation in Minds

    OpenAIRE

    Rácz, Attila

    2015-01-01

    In this paper, I explore socio-spatial segregation from a particular perspective, which may probably be considered a novelty in the investigation of spatial social patterns, as it focuses on questions such as: What kind of distinction occurs between socio-spatial patterns designated by statistical data and the cognitive representations of those patterns in people's minds? and What explains these diff erences, and what kind of impact can they generate?

  8. Chromosome Bridges Maintain Kinetochore-Microtubule Attachment throughout Mitosis and Rarely Break during Anaphase.

    Science.gov (United States)

    Pampalona, Judit; Roscioli, Emanuele; Silkworth, William T; Bowden, Brent; Genescà, Anna; Tusell, Laura; Cimini, Daniela

    2016-01-01

    Accurate chromosome segregation during cell division is essential to maintain genome stability, and chromosome segregation errors are causally linked to genetic disorders and cancer. An anaphase chromosome bridge is a particular chromosome segregation error observed in cells that enter mitosis with fused chromosomes/sister chromatids. The widely accepted Breakage/Fusion/Bridge cycle model proposes that anaphase chromosome bridges break during mitosis to generate chromosome ends that will fuse during the following cell cycle, thus forming new bridges that will break, and so on. However, various studies have also shown a link between chromosome bridges and aneuploidy and/or polyploidy. In this study, we investigated the behavior and properties of chromosome bridges during mitosis, with the idea to gain insight into the potential mechanism underlying chromosome bridge-induced aneuploidy. We find that only a small number of chromosome bridges break during anaphase, whereas the rest persist through mitosis into the subsequent cell cycle. We also find that the microtubule bundles (k-fibers) bound to bridge kinetochores are not prone to breakage/detachment, thus supporting the conclusion that k-fiber detachment is not the cause of chromosome bridge-induced aneuploidy. Instead, our data suggest that while the microtubules bound to the kinetochores of normally segregating chromosomes shorten substantially during anaphase, the k-fibers bound to bridge kinetochores shorten only slightly, and may even lengthen, during anaphase. This causes some of the bridge kinetochores/chromosomes to lag behind in a position that is proximal to the cell/spindle equator and may cause the bridged chromosomes to be segregated into the same daughter nucleus or to form a micronucleus.

  9. Towards understanding the molecular basis of bacterial DNA segregation

    DEFF Research Database (Denmark)

    Leonard, Thomas A.; Møller-Jensen, Jakob; Löwe, Jan

    2005-01-01

    Bacteria ensure the fidelity of genetic inheritance by the coordinated control of chromosome segregation and cell division. Here, we review the molecules and mechanisms that govern the correct subcellular positioning and rapid separation of newly replicated chromosomes and plasmids towards the cell...... poles and, significantly, the emergence of mitotic-like machineries capable of segregating plasmid DNA. We further describe surprising similarities between proteins involved in DNA partitioning (ParA/ParB) and control of cell division (MinD/MinE), suggesting a mechanism for intracellular positioning...... common to the two processes. Finally, we discuss the role that the bacterial cytoskeleton plays in DNA partitioning and the missing link between prokaryotes and eukaryotes that is bacterial mechano-chemical motor proteins. Udgivelsesdato: Mar 29...

  10. How to build segregation complexes in bacteria: Use bridges

    OpenAIRE

    Funnell, Barbara E.

    2014-01-01

    This perspective discusses the novel molecular mechanism of ParB spreading that is reported by Graham et al. (this issue). Using single-molecule analysis, Graham et al. found that Bacillus subtilis ParB proteins use a previously uncharacterized looping and bridging activity to assemble three-dimensional nucleoprotein complexes with DNA flanking the parS site. Formation of this higher-order ParB/parS complex is necessary for SMC condensin complex recruitment and chromosome segregation.

  11. Conditional Mutations in the Mitotic Chromosome Binding Function of the Bovine Papillomavirus Type 1 E2 Protein

    OpenAIRE

    Zheng, Peng-Sheng; Brokaw, Jane; Alison A McBride

    2005-01-01

    The papillomavirus E2 protein is required for viral transcriptional regulation, DNA replication and genome segregation. We have previously shown that the E2 transactivator protein and BPV1 genomes are associated with mitotic chromosomes; E2 links the genomes to cellular chromosomes to ensure efficient segregation to daughter nuclei. The transactivation domain of the E2 protein is necessary and sufficient for association of the E2 protein with mitotic chromosomes. To determine which residues o...

  12. Patterns of Residential Segregation.

    Directory of Open Access Journals (Sweden)

    Rémi Louf

    Full Text Available The spatial distribution of income shapes the structure and organisation of cities and its understanding has broad societal implications. Despite an abundant literature, many issues remain unclear. In particular, all definitions of segregation are implicitely tied to a single indicator, usually rely on an ambiguous definition of income classes, without any consensus on how to define neighbourhoods and to deal with the polycentric organization of large cities. In this paper, we address all these questions within a unique conceptual framework. We avoid the challenge of providing a direct definition of segregation and instead start from a definition of what segregation is not. This naturally leads to the measure of representation that is able to identify locations where categories are over- or underrepresented. From there, we provide a new measure of exposure that discriminates between situations where categories co-locate or repel one another. We then use this feature to provide an unambiguous, parameter-free method to find meaningful breaks in the income distribution, thus defining classes. Applied to the 2014 American Community Survey, we find 3 emerging classes-low, middle and higher income-out of the original 16 income categories. The higher-income households are proportionally more present in larger cities, while lower-income households are not, invalidating the idea of an increased social polarisation. Finally, using the density-and not the distance to a center which is meaningless in polycentric cities-we find that the richer class is overrepresented in high density zones, especially for larger cities. This suggests that density is a relevant factor for understanding the income structure of cities and might explain some of the differences observed between US and European cities.

  13. Patterns of Residential Segregation.

    Science.gov (United States)

    Louf, Rémi; Barthelemy, Marc

    2016-01-01

    The spatial distribution of income shapes the structure and organisation of cities and its understanding has broad societal implications. Despite an abundant literature, many issues remain unclear. In particular, all definitions of segregation are implicitely tied to a single indicator, usually rely on an ambiguous definition of income classes, without any consensus on how to define neighbourhoods and to deal with the polycentric organization of large cities. In this paper, we address all these questions within a unique conceptual framework. We avoid the challenge of providing a direct definition of segregation and instead start from a definition of what segregation is not. This naturally leads to the measure of representation that is able to identify locations where categories are over- or underrepresented. From there, we provide a new measure of exposure that discriminates between situations where categories co-locate or repel one another. We then use this feature to provide an unambiguous, parameter-free method to find meaningful breaks in the income distribution, thus defining classes. Applied to the 2014 American Community Survey, we find 3 emerging classes-low, middle and higher income-out of the original 16 income categories. The higher-income households are proportionally more present in larger cities, while lower-income households are not, invalidating the idea of an increased social polarisation. Finally, using the density-and not the distance to a center which is meaningless in polycentric cities-we find that the richer class is overrepresented in high density zones, especially for larger cities. This suggests that density is a relevant factor for understanding the income structure of cities and might explain some of the differences observed between US and European cities. PMID:27315283

  14. Mitotic chromosome compaction via active loop extrusion

    Science.gov (United States)

    Goloborodko, Anton; Imakaev, Maxim; Marko, John; Mirny, Leonid; MIT-Northwestern Team

    During cell division, two copies of each chromosome are segregated from each other and compacted more than hundred-fold into the canonical X-shaped structures. According to earlier microscopic observations and the recent Hi-C study, chromosomes are compacted into arrays of consecutive loops of ~100 kilobases. Mechanisms that lead to formation of such loop arrays are largely unknown. Here we propose that, during cell division, chromosomes can be compacted by enzymes that extrude loops on chromatin fibers. First, we use computer simulations and analytical modeling to show that a system of loop-extruding enzymes on a chromatin fiber self-organizes into an array of consecutive dynamic loops. Second, we model the process of loop extrusion in 3D and show that, coupled with the topo II strand-passing activity, it leads to robust compaction and segregation of sister chromatids. This mechanism of chromosomal condensation and segregation does not require additional proteins or specific DNA markup and is robust against variations in the number and properties of such loop extruding enzymes. Work at NU was supported by the NSF through Grants DMR-1206868 and MCB-1022117, and by the NIH through Grants GM105847 and CA193419. Work at MIT was supported by the NIH through Grants GM114190 R01HG003143.

  15. Chromosome assortment in Saccharum.

    Science.gov (United States)

    Al-Janabi, S M; Honeycutt, R J; Sobral, B W

    1994-12-01

    Recent work has revealed random chromosome pairing and assortment in Saccharum spontaneum L., the most widely distributed, and morphologically and cytologically variable of the species of Saccharum. This conclusion was based on the analysis of a segregating population from across between S. spontaneum 'SES 208' and a spontaneously-doubled haploid of itself, derived from anther culture. To determine whether polysomic inheritance is common in Saccharum and whether it is observed in a typical biparental cross, we studied chromosome pairing and assortment in 44 progeny of a cross between euploid, meiotically regular, 2n=80 forms of Saccharum officinarum 'LA Purple' and Saccharum robustum ' Mol 5829'. Papuan 2n=80 forms of S. robustum have been suggested as the immediate progenitor species for cultivated sugarcane (S. officinarum). A total of 738 loci in LA Purple and 720 loci in Mol 5829 were amplified and typed in the progeny by arbitrarily primed PCR using 45 primers. Fifty and 33 single-dose polymorphisms were identified in the S. officinarum and S. robustum genomes, respectively (χ 2 at 98%). Linkage analysis of single-dose polymorphisms in both genomes revealed linkages in repulsion and coupling phases. In the S. officinarum genome, a map hypothesis gave 7 linkage groups with 17 linked and 33 unlinked markers. Four of 13 pairwise linkages were in repulsion phase and 9 were in coupling phase. In the S. robustum genome, a map hypothesis gave 5 linkage groups, defined by 12 markers, with 21 markers unlinked, and 2 of 9 pairwise linkages were in repulsion phase. Therefore, complete polysomic inheritance was not observed in either species, suggesting that chromosomal behavior is different from that observed by linkage analysis of over 500 markers in the S. spontaneum map. Implications of this finding for evolution and breeding are discussed.

  16. Functions of spindle check-point and its relationship to chromosome instability

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    It is generally believed that the equal distribution of genetic materials to two daughter cells during mitosis is the key to cell health and development. During the dynamic process, spindle checkpoint plays a very important role in chromosome movements and final sister chromatid separation. The equal and precise segregation of chromosomes contributes to the genomic stability while aberrant separations result in chromosome instability that causes pathogenesis of certain diseases such as Down's syndrome and cancers. Kinetochore and its regulatory proteins consist of the spindle checkpoint and determine the spatial and temporal orders of chromosome segregation.

  17. Chromosome number reports in Astragalus sect. Onobrychoidei (Fabaceae from Iran

    Directory of Open Access Journals (Sweden)

    Massoud Ranjbar

    2015-01-01

    Full Text Available In this study, original mitotic chromosome counts have been presented for 10 populations belonging to 6 species of Astragalus sect. Onobrychoidei: A. aduncus, A. arguricus, A. cancellatus, A. lilacinus and A. vegetus. All taxa were diploid and possessed 2n = 2x = 16 chromosome number, consistent with the proposed base number of x = 8. In addition, meiotic studies revealed chromosome number of 2n = 2x = 16 for A. aduncus21 and A. brevidens and also 2n = 4x = 32 for A. vegetus99. Although this taxon displayed regular bivalent pairing and chromosome segregation at meiosis, some abnormalities were observed.

  18. Multilevel Modeling of Social Segregation

    Science.gov (United States)

    Leckie, George; Pillinger, Rebecca; Jones, Kelvyn; Goldstein, Harvey

    2012-01-01

    The traditional approach to measuring segregation is based upon descriptive, non-model-based indices. A recently proposed alternative is multilevel modeling. The authors further develop the argument for a multilevel modeling approach by first describing and expanding upon its notable advantages, which include an ability to model segregation at a…

  19. The Dimensions of Residential Segregation.

    Science.gov (United States)

    Massey, Douglas S.; Denton, Nancy A.

    1988-01-01

    Evaluates 20 potential indicators of residential segregation using census data on Hispanics, Blacks, Asians, and non-Hispanic Whites in 60 U.S. metropolitan areas. Factor-analyzes the results to select a single best indicator for each of five dimensions of residential segregation. Contains 69 references and 22 statistical formulas. (SV)

  20. Shaping Segregation: Convexity vs. concavity

    NARCIS (Netherlands)

    Gonzalez, S.; Windows-Yule, C.R.; Luding, S.; Parker, D.J.; Thornton, A.R.

    2014-01-01

    Controlling segregation is both a practical and a theoretical challenge. In this Letter we demonstrate a manner in which rotation-induced segregation may be controlled by altering the geometry of the rotating containers in which granular systems are housed. Using a novel drum design comprising conca

  1. Patterns of residential segregation

    CERN Document Server

    Louf, Rémi

    2015-01-01

    The spatial distribution of income shapes the structure and organisation of cities and its understanding has broad societal implications. Despite an abundant literature, many issues remain however unclear: there is no clear definition of what segregation is, no unambiguous definition of income classes, no clear way to identify neighborhoods, and no method to deal with the polycentric organization of large cities. In this paper, we address all these questions within a unique theoretical framework. We assume that households belonging to the same class tend to live close to each other, and households from different classes tend to avoid one another. Applied to the US 2000 Census Income data, 3 distinct classes emerge from the clustering of the original 16 income classes. Using these unambiguously defined classes, we cluster together contiguous similar areas and find that the number of clusters for each category scales with the city population, an effect that is more pronounced for rich households. Finally, using...

  2. A Question of Segregation

    DEFF Research Database (Denmark)

    Quedas, Fátima; Ponte, João; Trindade, Carlos;

    2016-01-01

    supply chain, rather than just segregation at the start, if bread is to be sold with a GMO content below the 0.9 per cent threshold level. Alternatively, retailers can label their bread. This might be a cheaper solution and as a study from Switzerland shows may not result in adverse consumer reaction.......We describe the maize supply chain in Portugal for maize bread, a traditional bread type. As this bread is not labelled as ‘contains genetically modified organisms’ it should not contain more than 0.9 per cent genetically modified ingredients. On the basis of interviews we identify a general lack...... of documentation of the presence or absence of genetically modified ingredients along the complete supply chain (farmers, traders, mills and bakeries). Part of this deficiency is probably driven by a lack of awareness of the labelling rules at the end of the supply chain. A test of maize bread showed that more...

  3. Effective formation of the segregation-competent complex determines successful partitioning of the bovine papillomavirus genome during cell division.

    Science.gov (United States)

    Silla, Toomas; Männik, Andres; Ustav, Mart

    2010-11-01

    Effective segregation of the bovine papillomavirus type 1 (BPV1), Epstein-Barr virus (EBV), and Kaposi's sarcoma-associated human herpesvirus type 8 (KSHV) genomes into daughter cells is mediated by a single viral protein that tethers viral genomes to host mitotic chromosomes. The linker proteins that mediate BPV1, EBV, and KSHV segregation are E2, LANA1, and EBNA1, respectively. The N-terminal transactivation domain of BPV1 E2 is responsible for chromatin attachment and subsequent viral genome segregation. Because E2 transcriptional activation and chromatin attachment functions are not mutually exclusive, we aimed to determine the requirement of these activities during segregation by analyzing chimeric E2 proteins. This approach allowed us to separate the two activities. Our data showed that attachment of the segregation protein to chromatin is not sufficient for proper segregation. Rather, formation of a segregation-competent complex which carries multiple copies of the segregation protein is required. Complementation studies of E2 functional domains indicated that chromatin attachment and transactivation functions must act in concert to ensure proper plasmid segregation. These data indicate that there are specific interactions between linker molecules and transcription factors/complexes that greatly increase segregation-competent complex formation. We also showed, using hybrid E2 molecules, that restored segregation function does not involve interactions with Brd4. PMID:20810736

  4. Entropy-driven spatial organization of highly confined polymers: Lessons for the bacterial chromosome

    Science.gov (United States)

    Jun, Suckjoon; Mulder, Bela

    2006-08-01

    Despite recent progress in visualization experiments, the mechanism underlying chromosome segregation in bacteria still remains elusive. Here we address a basic physical issue associated with bacterial chromosome segregation, namely the spatial organization of highly confined, self-avoiding polymers (of nontrivial topology) in a rod-shaped cell-like geometry. Through computer simulations, we present evidence that, under strong confinement conditions, topologically distinct domains of a polymer complex effectively repel each other to maximize their conformational entropy, suggesting that duplicated circular chromosomes could partition spontaneously. This mechanism not only is able to account for the spatial separation per se but also captures the major features of the spatiotemporal organization of the duplicating chromosomes observed in Escherichia coli and Caulobacter crescentus. bacterial chromosome segregation | Caulobacter crescentus | Escherichia coli | polymer physics

  5. Micronucleus formation causes perpetual unilateral chromosome inheritance in mouse embryos.

    Science.gov (United States)

    Vázquez-Diez, Cayetana; Yamagata, Kazuo; Trivedi, Shardul; Haverfield, Jenna; FitzHarris, Greg

    2016-01-19

    Chromosome segregation defects in cancer cells lead to encapsulation of chromosomes in micronuclei (MN), small nucleus-like structures within which dangerous DNA rearrangements termed chromothripsis can occur. Here we uncover a strikingly different consequence of MN formation in preimplantation development. We find that chromosomes from within MN become damaged and fail to support a functional kinetochore. MN are therefore not segregated, but are instead inherited by one of the two daughter cells. We find that the same MN can be inherited several times without rejoining the principal nucleus and without altering the kinetics of cell divisions. MN motion is passive, resulting in an even distribution of MN across the first two cell lineages. We propose that perpetual unilateral MN inheritance constitutes an unexpected mode of chromosome missegregation, which could contribute to the high frequency of aneuploid cells in mammalian embryos, but simultaneously may serve to insulate the early embryonic genome from chromothripsis.

  6. Chiasmatic and achiasmatic inverted meiosis of plants with holocentric chromosomes.

    Science.gov (United States)

    Cabral, Gabriela; Marques, André; Schubert, Veit; Pedrosa-Harand, Andrea; Schlögelhofer, Peter

    2014-01-01

    Meiosis is a specialized cell division in sexually reproducing organisms before gamete formation. Following DNA replication, the canonical sequence in species with monocentric chromosomes is characterized by reductional segregation of homologous chromosomes during the first and equational segregation of sister chromatids during the second meiotic division. Species with holocentric chromosomes employ specific adaptations to ensure regular disjunction during meiosis. Here we present the analysis of two closely related plant species with holocentric chromosomes that display an inversion of the canonical meiotic sequence, with the equational division preceding the reductional. In-depth analysis of the meiotic divisions of Rhynchospora pubera and R. tenuis reveals that during meiosis I sister chromatids are bi-oriented, display amphitelic attachment to the spindle and are subsequently separated. During prophase II, chromatids are connected by thin chromatin threads that appear instrumental for the regular disjunction of homologous non-sister chromatids in meiosis II. PMID:25295686

  7. Chromosome Microarray.

    Science.gov (United States)

    Anderson, Sharon

    2016-01-01

    Over the last half century, knowledge about genetics, genetic testing, and its complexity has flourished. Completion of the Human Genome Project provided a foundation upon which the accuracy of genetics, genomics, and integration of bioinformatics knowledge and testing has grown exponentially. What is lagging, however, are efforts to reach and engage nurses about this rapidly changing field. The purpose of this article is to familiarize nurses with several frequently ordered genetic tests including chromosomes and fluorescence in situ hybridization followed by a comprehensive review of chromosome microarray. It shares the complexity of microarray including how testing is performed and results analyzed. A case report demonstrates how this technology is applied in clinical practice and reveals benefits and limitations of this scientific and bioinformatics genetic technology. Clinical implications for maternal-child nurses across practice levels are discussed. PMID:27276104

  8. Mitotic Origins of Chromosomal Instability in Colorectal Cancer

    OpenAIRE

    Dalton, W. Brian; Yang, Vincent W.

    2007-01-01

    Mitosis is a crucial part of the cell cycle. A successful mitosis requires the proper execution of many complex cellular behaviors. Thus, there are many points at which mitosis may be disrupted. In cancer cells, chronic disruption of mitosis can lead to unequal segregation of chromosomes, a phenomenon known as chromosomal instability. A majority of colorectal tumors suffer from this instability, and recent studies have begun to reveal the specific ways in which mitotic defects promote chromos...

  9. Chromosome I duplications in Caenorhabditis elegans

    Energy Technology Data Exchange (ETDEWEB)

    McKim, K.S.; Rose, A.M. (Univ. of British Columbia, Vancouver (Canada))

    1990-01-01

    We have isolated and characterized 76 duplications of chromosome I in the genome of Caenorhabditis elegans. The region studied is the 20 map unit left half of the chromosome. Sixty-two duplications were induced with gamma radiation and 14 arose spontaneously. The latter class was apparently the result of spontaneous breaks within the parental duplication. The majority of duplications behave as if they are free. Three duplications are attached to identifiable sequences from other chromosomes. The duplication breakpoints have been mapped by complementation analysis relative to genes on chromosome I. Nineteen duplication breakpoints and seven deficiency breakpoints divide the left half of the chromosome into 24 regions. We have studied the relationship between duplication size and segregational stability. While size is an important determinant of mitotic stability, it is not the only one. We observed clear exceptions to a size-stability correlation. In addition to size, duplication stability may be influenced by specific sequences or chromosome structure. The majority of the duplications were stable enough to be powerful tools for gene mapping. Therefore the duplications described here will be useful in the genetic characterization of chromosome I and the techniques we have developed can be adapted to other regions of the genome.

  10. Cell division control by the Chromosomal Passenger Complex

    Energy Technology Data Exchange (ETDEWEB)

    Waal, Maike S. van der; Hengeveld, Rutger C.C.; Horst, Armando van der; Lens, Susanne M.A., E-mail: s.m.a.lens@umcutrecht.nl

    2012-07-15

    The Chromosomal Passenger Complex (CPC) consisting of Aurora B kinase, INCENP, Survivin and Borealin, is essential for genomic stability by controlling multiple processes during both nuclear and cytoplasmic division. In mitosis it ensures accurate segregation of the duplicated chromosomes by regulating the mitotic checkpoint, destabilizing incorrectly attached spindle microtubules and by promoting the axial shortening of chromosomal arms in anaphase. During cytokinesis the CPC most likely prevents chromosome damage by imposing an abscission delay when a chromosome bridge connects the two daughter cells. Moreover, by controlling proper cytoplasmic division, the CPC averts tetraploidization. This review describes recent insights on how the CPC is capable of conducting its various functions in the dividing cell to ensure chromosomal stability.

  11. Dispensability of the SAC Depends on the Time Window Required by Aurora B to Ensure Chromosome Biorientation

    Science.gov (United States)

    Monje-Casas, Fernando

    2015-01-01

    Aurora B and the spindle assembly checkpoint (SAC) collaborate to ensure the proper biorientation of chromosomes during mitosis. However, lack of Aurora B activity and inactivation of the SAC have a very different impact on chromosome segregation. This is most evident in Saccharomyces cerevisiae, since in this organism the lack of Aurora B is lethal and leads to severe aneuploidy problems, while the SAC is dispensable under normal growth conditions and mutants in this checkpoint do not show evident chromosome segregation defects. We demonstrate that the efficient repair of incorrect chromosome attachments by Aurora B during the initial stages of spindle assembly in budding yeast determines the lack of chromosome segregation defects in SAC mutants, and propose that the differential time window that Aurora B kinase requires to establish chromosome biorientation is the key factor that determines why some cells are more dependent on a functional SAC than others. PMID:26661752

  12. Can topology reshape segregation patterns?

    CERN Document Server

    Gandica, Yerali; Carletti, Timoteo

    2015-01-01

    We consider a metapopulation version of the Schelling model of segregation over several complex networks and lattice. We show that the segregation process is topology independent and hence it is intrinsic to the individual tolerance. The role of the topology is to fix the places where the segregation patterns emerge. In addition we address the question of the time evolution of the segregation clusters, resulting from different dynamical regimes of a coarsening process, as a function of the tolerance parameter. We show that the underlying topology may alter the early stage of the coarsening process, once large values of the tolerance are used, while for lower ones a different mechanism is at work and it results to be topology independent.

  13. School Desegregation and Residential Segregation.

    Science.gov (United States)

    Billingsley, Andrew; And Others

    1979-01-01

    This statement on school and residential segregation, signed by 38 educators and social scientists, was prepared for attorneys connected with litigation concerning the Dayton and Columbus school systems. (RLV)

  14. A physical approach to segregation and folding of the Caulobacter crescentus genome

    NARCIS (Netherlands)

    R.T. Dame; M. Tark-Dame; H Schiessel

    2011-01-01

    Bacterial genomes are functionally organized. This organization is dynamic and globally changing throughout the cell cycle. Upon initiation of replication of the chromosome, the two origins segregate and move towards their new location taking along the newly replicated genome. Caulobacter crescentus

  15. The fragile Y hypothesis: Y chromosome aneuploidy as a selective pressure in sex chromosome and meiotic mechanism evolution.

    Science.gov (United States)

    Blackmon, Heath; Demuth, Jeffery P

    2015-09-01

    Loss of the Y-chromosome is a common feature of species with chromosomal sex determination. However, our understanding of why some lineages frequently lose Y-chromosomes while others do not is limited. The fragile Y hypothesis proposes that in species with chiasmatic meiosis the rate of Y-chromosome aneuploidy and the size of the recombining region have a negative correlation. The fragile Y hypothesis provides a number of novel insights not possible under traditional models. Specifically, increased rates of Y aneuploidy may impose positive selection for (i) gene movement off the Y; (ii) translocations and fusions which expand the recombining region; and (iii) alternative meiotic segregation mechanisms (achiasmatic or asynaptic). These insights as well as existing evidence for the frequency of Y-chromosome aneuploidy raise doubt about the prospects for long-term retention of the human Y-chromosome despite recent evidence for stable gene content in older non-recombining regions.

  16. Residential Segregation in General Equilibrium

    OpenAIRE

    Bayer, Patrick; McMillan, Robert; Rueben, Kim

    2005-01-01

    This paper studies the causes and consequences of racial segregation using a new general equilibrium model that treats neighborhood compositions as endogenous. The model is estimated using unusually detailed restricted Census microdata covering the entire San Francisco Bay Area, and in combination with a rich array of econometric estimates, serves as a powerful tool for carrying out counterfactual simulations that shed light on the causes and consequences of segregation. In terms of causes, a...

  17. Heterogeneous Immigration, Segregation and Trade

    OpenAIRE

    Fabien Candau

    2011-01-01

    By introducing taste heterogeneity between mobile workers in a New Economic Geography (NEG) model where the housing price is the main driving force behind dispersion of workers we show that residential segregation and agglomeration are not the sole stable equilibria and that dispersion also emerges with trade liberalization. In addition we find that contrary to the Tiebout hypothesis where segregation is efficient, here it is the dispersed and mixed equilibrium which can be improving for all.

  18. A role for Aurora C in the chromosomal passenger complex during human preimplantation embryo development

    NARCIS (Netherlands)

    Santos, Margarida Avo; van de Werken, Christine; de Vries, Marieke; Jahr, Holger; Vromans, Martijn J. M.; Laven, Joop S. E.; Fauser, Bart C.; Kops, Geert J.; Lens, Susanne M.; Baart, Esther B.

    2011-01-01

    BACKGROUND: Human embryos generated by IVF demonstrate a high incidence of chromosomal segregation errors during the cleavage divisions. To analyse underlying molecular mechanisms, we investigated the behaviour of the chromosomal passenger complex (CPC) in human oocytes and embryos. This important m

  19. Probing CENP-E function in chromosome dynamics using small molecule inhibitor syntelin

    Institute of Scientific and Technical Information of China (English)

    Xia Ding; Tongge Zhu; Jiancun Zhang; Zhen Dou; Xuebiao Yao; Feng Yan; Phil Yao; Zhihong Yang; Weihong Wan; Xiwei Wang; Jing Liu; Xinjiao Gao; Ariane Abrieu

    2010-01-01

    @@ Dear Editor, Chromosome movements during mitosis are orchestrated primarily by the interaction of spindle microtubules with the kinetochore [1], the site for attachment of spindle microtubules to the centromere. The kinetochore has an active function in chromosomal segregation through microtubule-based motors located at or near it [1-2].

  20. School Segregation: The Case of Amsterdam.

    Science.gov (United States)

    Gramberg, Peter

    1998-01-01

    Deals with facets of school segregation in Amsterdam, a city in which two-thirds of youth have a non-native background. The role of residential segregation in the segregation of elementary schools and the importance of educational background in the segregation of secondary schools are discussed. There are implications for schooling in the United…

  1. A Revaluation of Indexes of Residential Segregation

    Science.gov (United States)

    Winship, Christopher

    1977-01-01

    Shows that there are at least two different perspectives from which residential segregation can be examined. Segregation can be measured as it deviates from a situation of complete desegregation or in terms of a situation in which there is random segregation in the city. New criteria for indexes of residential segregation are developed. (Author/JM)

  2. Occupational segregation of immigrant women in Spain

    OpenAIRE

    Coral del Río; Olga Alonso-Villar

    2010-01-01

    The aim of this paper is to analyze occupational segregation in the Spanish labor market from a gender and an immigration perspective. In doing so, several local and overall segregation measures are used. Our results suggest that immigrant women in Spain suffer a double segregation since segregation affects them to a greater extent than it does either native women or immigrant men. There are, however, remarkable discrepancies among the segregation of immigrant women depending on their region ...

  3. Assignment of the structural gene for the third component of human complement to chromosome 19.

    OpenAIRE

    Whitehead, A. S.; Solomon, E; Chambers, S.; Bodmer, W F; Povey, S; Fey, G

    1982-01-01

    The third component of complement (C3) is synthesized and secreted by cultured human primary fibroblasts. A monoclonal antibody having specificity for an antigenic determinant carried by human but not mouse C3 was used to study the continued expression of human C3 in three panels of independently derived human-mouse somatic cell hybrids. Expression of the human product was shown to segregate with human chromosome 19 and with no other chromosome or group of chromosomes. A unique-sequence human...

  4. Differential Management of the Replication Terminus Regions of the Two Vibrio cholerae Chromosomes during Cell Division

    OpenAIRE

    Gaëlle Demarre; Elisa Galli; Leila Muresan; Evelyne Paly; Ariane David; Christophe Possoz; François-Xavier Barre

    2014-01-01

    The replication terminus region (Ter) of the unique chromosome of most bacteria locates at mid-cell at the time of cell division. In several species, this localization participates in the necessary coordination between chromosome segregation and cell division, notably for the selection of the division site, the licensing of the division machinery assembly and the correct alignment of chromosome dimer resolution sites. The genome of Vibrio cholerae, the agent of the deadly human disease choler...

  5. Variations in the association of papillomavirus E2 proteins with mitotic chromosomes

    OpenAIRE

    Jaquelline G de Oliveira; Colf, Leremy A.; Alison A McBride

    2006-01-01

    The E2 protein segregates episomal bovine papillomavirus (BPV) genomes to daughter cells by tethering them to mitotic chromosomes, thus ensuring equal distribution and retention of viral DNA. To date, only the BPV1 E2 protein has been shown to bind to mitotic chromosomes. We assessed the localization of 13 different animal and human E2 proteins from seven papillomavirus genera, and we show that most of them are stably bound to chromosomes throughout mitosis. Furthermore, in contrast to the ra...

  6. Segregation distortion in chicken and the evolutionary consequences of female meiotic drive in birds

    DEFF Research Database (Denmark)

    Axelsson, Erik Gunnar; Albrechtsen, Anders; Van, A. P.;

    2010-01-01

    termed female meiotic drive. We are aware of two chromosomal components, centromeres and telomeres, which share the potential to influence chromosome movement during meioses and make the following predictions based on the presence of female meiotic drive: (1) centromere-binding proteins should experience...... rapid evolution as a result of a conflict between driving centromeres and the rest of the genome; and (2) segregation patterns should be skewed near centromeres and telomeres. To test these predictions, we first analyze the molecular evolution of seven centromere-binding proteins in nine divergent bird....... By simulating fair Mendelian meioses, we locate chromosomal regions with statistically significant transmission ratio distortion. One region is located near the centromere on chromosome 1 and a second region is located near the telomere on the p-arm of chromosome 1. Although these observations do not provide...

  7. Grain Boundary Segregation in Metals

    CERN Document Server

    Lejcek, Pavel

    2010-01-01

    Grain boundaries are important structural components of polycrystalline materials used in the vast majority of technical applications. Because grain boundaries form a continuous network throughout such materials, their properties may limit their practical use. One of the serious phenomena which evoke these limitations is the grain boundary segregation of impurities. It results in the loss of grain boundary cohesion and consequently, in brittle fracture of the materials. The current book deals with fundamentals of grain boundary segregation in metallic materials and its relationship to the grain boundary structure, classification and other materials properties.

  8. Tailings philosophies : to segregate or not to segregate

    Energy Technology Data Exchange (ETDEWEB)

    Wells, P.S. [Suncor Energy, Fort McMurray, AB (Canada)

    2010-07-01

    Traditional technologies for treating oil sands tailings include the segregation of of tailings when discharged into water-filled ponds. The coarser tailings form long beaches. However, the percentage of silts and clays that remain suspended within the water column pose significant challenges to oil sands operators, and contribute to water losses and increases in storage volume. This paper discussed new technologies developed to identify the tailings materials that contribute to the problem and methods designed to isolate and treat the materials. Treatment material balances, process water balances, and material handling requirements for the technologies were evaluated and compared. Three scenarios were considered: (1) a sub-aqueous beaching scenario where tailings were produced by extraction and pumped to a beach storage area for dewatering through self-drainage; (2) a non-segregated tailings (NST) scenario that used mature fine tailings (MFT) drying; (3) and a segregated stream scenario where MFT drying was used where tailings were deposited in traditional tailings ponds. Results of the study showed that the segregated stream tailings treatment system was preferred to NST treatment system. Options for sub-aerial NST deposition may overcome the volume discrepancies between treating fines as well as the required volumes of coarser materials. 5 refs., 2 tabs., 2 figs.

  9. Chromatids segregate without centrosomes during Caenorhabditis elegans mitosis in a Ran- and CLASP-dependent manner.

    Science.gov (United States)

    Nahaboo, Wallis; Zouak, Melissa; Askjaer, Peter; Delattre, Marie

    2015-06-01

    During mitosis, chromosomes are connected to a microtubule-based spindle. Current models propose that displacement of the spindle poles and/or the activity of kinetochore microtubules generate mechanical forces that segregate sister chromatids. Using laser destruction of the centrosomes during Caenorhabditis elegans mitosis, we show that neither of these mechanisms is necessary to achieve proper chromatid segregation. Our results strongly suggest that an outward force generated by the spindle midzone, independently of centrosomes, is sufficient to segregate chromosomes in mitotic cells. Using mutant and RNAi analysis, we show that the microtubule-bundling protein SPD-1/MAP-65 and BMK-1/kinesin-5 act as a brake opposing the force generated by the spindle midzone. Conversely, we identify a novel role for two microtubule-growth and nucleation agents, Ran and CLASP, in the establishment of the centrosome-independent force during anaphase. Their involvement raises the interesting possibility that microtubule polymerization of midzone microtubules is continuously required to sustain chromosome segregation during mitosis.

  10. ASAR15, A cis-acting locus that controls chromosome-wide replication timing and stability of human chromosome 15.

    Directory of Open Access Journals (Sweden)

    Nathan Donley

    2015-01-01

    Full Text Available DNA replication initiates at multiple sites along each mammalian chromosome at different times during each S phase, following a temporal replication program. We have used a Cre/loxP-based strategy to identify cis-acting elements that control this replication-timing program on individual human chromosomes. In this report, we show that rearrangements at a complex locus at chromosome 15q24.3 result in delayed replication and structural instability of human chromosome 15. Characterization of this locus identified long, RNA transcripts that are retained in the nucleus and form a "cloud" on one homolog of chromosome 15. We also found that this locus displays asynchronous replication that is coordinated with other random monoallelic genes on chromosome 15. We have named this locus ASynchronous replication and Autosomal RNA on chromosome 15, or ASAR15. Previously, we found that disruption of the ASAR6 lincRNA gene results in delayed replication, delayed mitotic condensation and structural instability of human chromosome 6. Previous studies in the mouse found that deletion of the Xist gene, from the X chromosome in adult somatic cells, results in a delayed replication and instability phenotype that is indistinguishable from the phenotype caused by disruption of either ASAR6 or ASAR15. In addition, delayed replication and chromosome instability were detected following structural rearrangement of many different human or mouse chromosomes. These observations suggest that all mammalian chromosomes contain similar cis-acting loci. Thus, under this scenario, all mammalian chromosomes contain four distinct types of essential cis-acting elements: origins, telomeres, centromeres and "inactivation/stability centers", all functioning to promote proper replication, segregation and structural stability of each chromosome.

  11. Filament depolymerization can explain chromosome pulling during bacterial mitosis.

    Directory of Open Access Journals (Sweden)

    Edward J Banigan

    2011-09-01

    Full Text Available Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole, binds to a ParB-decorated chromosome, and then retracts via disassembly, pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that disassembles it. We perform Brownian dynamics simulations with a simple, physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is "self-diffusiophoretic": by disassembling ParA, ParB generates a ParA concentration gradient so that the ParA concentration is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is most robust when ParB binds side-on to ParA filaments. In this case, robust translocation occurs over a wide parameter range and is controlled by a single dimensionless quantity: the product of the rate of ParA disassembly and a characteristic relaxation time of the chromosome. This time scale measures the time it takes for the chromosome to recover its average shape after it is has been pulled. Our results suggest explanations for observed phenomena such as segregation failure, filament-length-dependent translocation velocity, and chromosomal compaction.

  12. Linking Dichotomous Segregation with Multi-group Segregation: Weighted Segregation Ratios in Selected U. S. Metropolitan Areas

    OpenAIRE

    Hao, Lingxin; Fong, Eric

    2011-01-01

    The U. S. residential landscape is increasingly multi-racial and multi-ethnic, giving rise to the question of how to compare dichotomous segregation among multiple groups living in the same area. To address the problem in the existing dichotomous approach, which offers no common basis for comparing dichotomous segregation among multiple groups, this paper develops a weighted segregation ratio approach based on Theil's segregation index and its additive decomposability. This approach can be us...

  13. Nonequilibrium Segregation in Petroleum Reservoirs

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Stenby, Erling Halfdan

    1999-01-01

    We analyse adsorption of a multicomponent mixture at high pressure on the basis of the potential theory of adsorption. The adsorbate is considered as a segregated mixture in the external field produced by a solid adsorbent. we derive an analytical equation for the thickness of a multicomponent film...

  14. Sexual orientation, prejudice and segregation

    NARCIS (Netherlands)

    E. Plug; D. Webbink; N. Martin

    2014-01-01

    This article examines whether gay and lesbian workers sort into tolerant occupations. With information on sexual orientation, prejudice, and occupational choice taken from Australian Twin Registers, we find that gays and lesbians shy away from prejudiced occupations. We show that our segregation res

  15. Gender Segregation: Separate but Effective?

    Science.gov (United States)

    Holthouse, David

    2010-01-01

    In 2002, only 11 public schools in the United States had gender-segregated classrooms. As of December 2009, there were more than 550. The movement is based on the hypothesis that hard-wired differences in the ways that male and female brains develop and function in childhood through adolescence require classrooms in which boys and girls are not…

  16. Why Our Schools Are Segregated

    Science.gov (United States)

    Rothstein, Richard

    2013-01-01

    "Residential segregation's causes are both knowable and known," writes Richard Rothstein. According to Rothstein, those causes are "20th century federal, state, and local policies explicitly designed to separate the races." Even seasoned policymakers are convinced that the residential isolation of low-income black children…

  17. Linking integration and residential segregation

    NARCIS (Netherlands)

    Bolt, G.S.; Özüekren, A.S.; Phillips, Deborah

    2010-01-01

    In the introduction to this special issue of JEMS, we question the strong link which is often made between the integration of minority ethnic groups and their residential segregation. In the literature on neighbourhood effects, the residential concentration of minorities is seen as a major obstacle

  18. The Geographic Scale of Metropolitan Racial Segregation

    OpenAIRE

    Reardon, Sean F.; Matthews, Stephen A.; O’Sullivan, David; Lee, Barrett A.; Firebaugh, Glenn; Farrell, Chad R.; BISCHOFF, KENDRA

    2008-01-01

    This article addresses an aspect of racial residential segregation that has been largely ignored in prior work: the issue of geographic scale. In some metropolitan areas, racial groups are segregated over large regions, with predominately white regions, predominately black regions, and so on, whereas in other areas, the separation of racial groups occurs over much shorter distances. Here we develop an approach—featuring the segregation profile and the corresponding macro/micro segregation rat...

  19. Measuring segregation: an activity space approach

    OpenAIRE

    Wong, David W. S.; Shaw, Shih-Lung

    2011-01-01

    While the literature clearly acknowledges that individuals may experience different levels of segregation across their various socio-geographical spaces, most measures of segregation are intended to be used in the residential space. Using spatially aggregated data to evaluate segregation in the residential space has been the norm and thus individual’s segregation experiences in other socio-geographical spaces are often de-emphasized or ignored. This paper attempts to provide a more comprehens...

  20. Is Segregation Bad for Your Health?

    OpenAIRE

    Kramer, Michael R; Hogue, Carol R.

    2009-01-01

    For decades, racial residential segregation has been observed to vary with health outcomes for African Americans, although only recently has interest increased in the public health literature. Utilizing a systematic review of the health and social science literature, the authors consider the segregation-health association through the lens of 4 questions of interest to epidemiologists: How is segregation best measured? Is the segregation-health association socially or biologically plausible? W...

  1. The Smc5-Smc6 complex is required to remove chromosome junctions in meiosis.

    Directory of Open Access Journals (Sweden)

    Sarah Farmer

    Full Text Available Meiosis, a specialized cell division with a single cycle of DNA replication round and two consecutive rounds of nuclear segregation, allows for the exchange of genetic material between parental chromosomes and the formation of haploid gametes. The structural maintenance of chromosome (SMC proteins aid manipulation of chromosome structures inside cells. Eukaryotic SMC complexes include cohesin, condensin and the Smc5-Smc6 complex. Meiotic roles have been discovered for cohesin and condensin. However, although Smc5-Smc6 is known to be required for successful meiotic divisions, the meiotic functions of the complex are not well understood. Here we show that the Smc5-Smc6 complex localizes to specific chromosome regions during meiotic prophase I. We report that meiotic cells lacking Smc5-Smc6 undergo catastrophic meiotic divisions as a consequence of unresolved linkages between chromosomes. Surprisingly, meiotic segregation defects are not rescued by abrogation of Spo11-induced meiotic recombination, indicating that at least some chromosome linkages in smc5-smc6 mutants originate from other cellular processes. These results demonstrate that, as in mitosis, Smc5-Smc6 is required to ensure proper chromosome segregation during meiosis by preventing aberrant recombination intermediates between homologous chromosomes.

  2. 17 CFR 31.12 - Segregation.

    Science.gov (United States)

    2010-04-01

    ... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Segregation. 31.12 Section 31....12 Segregation. (a) Any person that accepts leverage customer funds from a leverage customer to enter.... Notwithstanding the foregoing, a leverage transaction merchant may exclude from its segregation...

  3. 18 CFR 401.113 - Segregable materials.

    Science.gov (United States)

    2010-04-01

    ... 18 Conservation of Power and Water Resources 2 2010-04-01 2010-04-01 false Segregable materials. 401.113 Section 401.113 Conservation of Power and Water Resources DELAWARE RIVER BASIN COMMISSION... Segregable materials. Any reasonably segregable portion of a record shall be provided to any...

  4. Lack of response to unaligned chromosomes in mammalian female gametes.

    Science.gov (United States)

    Sebestova, Jaroslava; Danylevska, Anna; Novakova, Lucia; Kubelka, Michal; Anger, Martin

    2012-08-15

    Chromosome segregation errors are highly frequent in mammalian female meiosis, and their incidence gradually increases with maternal age. The fate of aneuploid eggs is obviously dependent on the stringency of mechanisms for detecting unattached or repairing incorrectly attached kinetochores. In case of their failure, the newly formed embryo will inherit the impaired set of chromosomes, which will have severe consequences for its further development. Whether spindle assembly checkpoint (SAC) in oocytes is capable of arresting cell cycle progression in response to unaligned kinetochores was discussed for a long time. It is known that abolishing SAC increases frequency of chromosome segregation errors and causes precocious entry into anaphase; SAC, therefore, seems to be essential for normal chromosome segregation in meiosis I. However, it was also reported that for anaphase-promoting complex (APC) activation, which is a prerequisite for entering anaphase; alignment of only a critical mass of kinetochores on equatorial plane is sufficient. This indicates that the function of SAC and of cooperating chromosome attachment correction mechanisms in oocytes is different from somatic cells. To analyze this phenomenon, we used live cell confocal microscopy to monitor chromosome movements, spindle formation, APC activation and polar body extrusion (PBE) simultaneously in individual oocytes at various time points during first meiotic division. Our results, using oocytes from aged animals and interspecific crosses, demonstrate that multiple unaligned kinetochores and severe congression defects are tolerated at the metaphase to anaphase transition, although such cells retain sensitivity to nocodazole. This indicates that checkpoint mechanisms, operating in oocytes at this point, are essential for accurate timing of APC activation in meiosis I, but they are insufficient in detection or correction of unaligned chromosomes, preparing thus conditions for propagation of the aneuploidy

  5. Undetected sex chromosome aneuploidy by chromosomal microarray.

    Science.gov (United States)

    Markus-Bustani, Keren; Yaron, Yuval; Goldstein, Myriam; Orr-Urtreger, Avi; Ben-Shachar, Shay

    2012-11-01

    We report on a case of a female fetus found to be mosaic for Turner syndrome (45,X) and trisomy X (47,XXX). Chromosomal microarray analysis (CMA) failed to detect the aneuploidy because of a normal average dosage of the X chromosome. This case represents an unusual instance in which CMA may not detect chromosomal aberrations. Such a possibility should be taken into consideration in similar cases where CMA is used in a clinical setting.

  6. Stretching the rules: monocentric chromosomes with multiple centromere domains.

    Science.gov (United States)

    Neumann, Pavel; Navrátilová, Alice; Schroeder-Reiter, Elizabeth; Koblížková, Andrea; Steinbauerová, Veronika; Chocholová, Eva; Novák, Petr; Wanner, Gerhard; Macas, Jiří

    2012-01-01

    The centromere is a functional chromosome domain that is essential for faithful chromosome segregation during cell division and that can be reliably identified by the presence of the centromere-specific histone H3 variant CenH3. In monocentric chromosomes, the centromere is characterized by a single CenH3-containing region within a morphologically distinct primary constriction. This region usually spans up to a few Mbp composed mainly of centromere-specific satellite DNA common to all chromosomes of a given species. In holocentric chromosomes, there is no primary constriction; the centromere is composed of many CenH3 loci distributed along the entire length of a chromosome. Using correlative fluorescence light microscopy and high-resolution electron microscopy, we show that pea (Pisum sativum) chromosomes exhibit remarkably long primary constrictions that contain 3-5 explicit CenH3-containing regions, a novelty in centromere organization. In addition, we estimate that the size of the chromosome segment delimited by two outermost domains varies between 69 Mbp and 107 Mbp, several factors larger than any known centromere length. These domains are almost entirely composed of repetitive DNA sequences belonging to 13 distinct families of satellite DNA and one family of centromeric retrotransposons, all of which are unevenly distributed among pea chromosomes. We present the centromeres of Pisum as novel "meta-polycentric" functional domains. Our results demonstrate that the organization and DNA composition of functional centromere domains can be far more complex than previously thought, do not require single repetitive elements, and do not require single centromere domains in order to segregate properly. Based on these findings, we propose Pisum as a useful model for investigation of centromere architecture and the still poorly understood role of repetitive DNA in centromere evolution, determination, and function. PMID:22737088

  7. Organizing the bacterial chromosome for division

    Science.gov (United States)

    Broedersz, Chase

    2014-03-01

    The chromosome is highly organized in space in many bacteria, although the origin and function of this organization remain unclear. This organization is further complicated by the necessity for chromosome replication and segregation. Partitioning proteins of the ParABS system mediate chromosomal and plasmid segregation in a variety of bacteria. This segregation machinery includes a large ParB-DNA complex consisting of roughly 1000 ParB dimers, which localizes around one or a few centromere-like parS sites near the origin of replication. Despite the apparent simplicity of this segregation machinery as compared to eukaryotic segregations systems, puzzles remain: In particular, what is the nature of interactions among DNA-bound ParB proteins, and how do these determine the organizational and functional properties of the ParB-DNA partitioning complex? A crucial aspect of this question is whether ParB spreads along the DNA to form a filamentous protein-DNA complex with a 1D character, or rather assembles to form a 3D complex on the DNA. Furthermore, it remains unclear how the presence of only one or even a few parS sites can lead to robust formation and localization of such a large protein-DNA complex. We developed a simple model for interacting proteins on DNA, and found that a combination of 1D spreading bonds and a 3D bridging bond between ParB proteins constitutes the minimal model for condensation of a 3D ParB-DNA complex. These combined interactions provide an effective surface tension that prevents fragmentation of the ParB-DNA complex. Thus, ParB spreads to form multiple 1D domains on the DNA, connected in 3D by bridging interactions to assemble into a 3D ParB-DNA condensate. Importantly, this model accounts for recent experiments on ParB-induced gene-silencing and the effect of a DNA ``roadblock'' on ParB localization. Furthermore, our model provides a simple mechanism to explain how a single parS site is both necessary and sufficient for the formation and

  8. On the dynamics of segregation

    OpenAIRE

    Jofre-Monseny, Jordi; Dahlberg, Matz; Fredriksson, Peter

    2012-01-01

    Card et al (2008a) formalize a model of ethnic residential segregation where an ethnically mixed neighborhood is dynamically stable until its minority share reaches a threshold (the tipping point). Once the neighborhood has surpassed the tipping point, it will experience massive white flight. These authors propose methods to identify tipping points and, using population counts at the US Census tract level, find that tipping is a salient feature of neighborhood dynamics. The objective of this ...

  9. A cohesin-based structural platform supporting homologous chromosome pairing in meiosis.

    Science.gov (United States)

    Ding, Da-Qiao; Haraguchi, Tokuko; Hiraoka, Yasushi

    2016-08-01

    The pairing and recombination of homologous chromosomes during the meiotic prophase is necessary for the accurate segregation of chromosomes in meiosis. However, the mechanism by which homologous chromosomes achieve this pairing has remained an open question. Meiotic cohesins have been shown to affect chromatin compaction; however, the impact of meiotic cohesins on homologous pairing and the fine structures of cohesion-based chromatin remain to be determined. A recent report using live-cell imaging and super-resolution microscopy demonstrated that the lack of meiotic cohesins alters the chromosome axis structures and impairs the pairing of homologous chromosomes. These results suggest that meiotic cohesin-based chromosome axis structures are crucial for the pairing of homologous chromosomes. PMID:26856595

  10. Filament depolymerization can pull a chromosome during bacterial mitosis

    Science.gov (United States)

    Banigan, Edward; Gelbart, Michael; Gitai, Zemer; Liu, Andrea; Wingreen, Ned

    2011-03-01

    Chromosome segregation is fundamental to all cells, but the force-generating mechanisms underlying chromosome translocation in bacteria remain mysterious. Caulobacter crescentus utilizes a depolymerization-driven process in which a ParA protein structure elongates from the new cell pole and binds to a ParB-decorated chromosome, and then retracts via disassembly, thus pulling the chromosome across the cell. This poses the question of how a depolymerizing structure can robustly pull the chromosome that is disassembling it. We perform Brownian dynamics simulations with a simple and physically consistent model of the ParABS system. The simulations suggest that the mechanism of translocation is ``self-diffusiophoretic'': by disassembling ParA, ParB generates a ParA concentration gradient so that the concentration of ParA is higher in front of the chromosome than behind it. Since the chromosome is attracted to ParA via ParB, it moves up the ParA gradient and across the cell. We find that translocation is controlled by the product of an effective relaxation time for the chromosome and the rate of ParA disassembly. Our results provide a physical explanation of the mechanism of depolymerization-driven translocation and suggest physical explanations for recent experimental observations.

  11. Development of a novel HAC-based "gain of signal" quantitative assay for measuring chromosome instability (CIN) in cancer cells

    OpenAIRE

    Kim, Jung Hyun; Lee, Hee Sheung; Lee, Nicholas C.O.; Goncharov, Nikolay V.; Kumeiko, Vadim; Masumoto, Hiroshi; Earnshaw, William C.; Kouprina, Natalay; Larionov, Vladimir

    2016-01-01

    Accumulating data indicates that chromosome instability (CIN) common to cancer cells can be used as a target for cancer therapy. At present the rate of chromosome mis-segregation is quantified by laborious techniques such as coupling clonal cell analysis with karyotyping or fluorescence in situ hybridization (FISH). Recently, a novel assay was developed based on the loss of a non-essential human artificial chromosome (HAC) carrying a constitutively expressed EGFP transgene ("loss of signal" a...

  12. Fetal chromosome analysis: screening for chromosome disease?

    DEFF Research Database (Denmark)

    Philip, J; Tabor, Ann; Bang, J;

    1983-01-01

    The aim of the study was to investigate the rationale of the current indications for fetal chromosome analysis. 5372 women had 5423 amniocentesis performed, this group constituting a consecutive sample at the chromosome laboratory, Rigshospitalet, Copenhagen from March 1973 to September 1980 (Group...... A + B). Pregnant women 35 years of age, women who previously had a chromosomally abnormal child, families with translocation carriers or other heritable chromosomal disease, families where the father was 50 years or more and women in families with a history of Down's syndrome (group A), were compared...... to women having amniocentesis, although considered not to have any increased risk of fetal chromosome abnormality (1390 pregnancies, group B). They were also compared with 750 consecutive pregnancies in women 25-34 years of age, in whom all heritable diseases were excluded (group C). The risk of unbalanced...

  13. Chromosome Disorder Outreach

    Science.gov (United States)

    ... BLOG Join Us Donate You are not alone. Chromosome Disorder Outreach, Inc. is a non-profit organization, ... Support For all those diagnosed with any rare chromosome disorder. Since 1992, CDO has supported the parents ...

  14. Assignment of genes encoding metallothioneins I and II to Chinese hamster chromosomes 3. Evidence for the role of chromosome rearrangement in gene amplification

    Energy Technology Data Exchange (ETDEWEB)

    Stallings, R.L.; Munk, A.C.; Longmire, J.L.; Hildebrand, C.E.; Crawford, B.D.

    1984-12-01

    Cadmium resistant (Cd/sup r/) variants with coordinately amplified metallothionein I and II (MTI and MTII) genes have been derived from both Chinese hamster ovary and near-euploid Chinese hamster cell lines. Cytogenetic analyses of Cd/sup r/ variants consistently revealed breakage and rearrangement involving chromosome 3p. In situ hybridization with Chinese hamster MT-encoding cDNA probe localized amplified MT gene sequences near the translocation breakpoint involving chromosome 3p. These observations suggested that both functionally related, isometallothionein loci are linked on Chinese hamster chromosome 3. Southern blot analyses of DNAs isolated from a panel of Chinese hamster x mouse somatic cell hybrids which segregate hamster chromosomes confirmed that both MTI and MTII are located on chromosome 3. The authors speculate that rearrangement of chromosome 3p could be causally involved with the amplification of MT genes in Cd/sup r/ hamster cell lines. 34 references, 3 figures, 1 table.

  15. ZEBRAFISH CHROMOSOME-BANDING

    NARCIS (Netherlands)

    PIJNACKER, LP; FERWERDA, MA

    1995-01-01

    Banding techniques were carried out on metaphase chromosomes of zebrafish (Danio rerio) embryos. The karyotypes with the longest chromosomes consist of 12 metacentrics, 26 submetacentrics, and 12 subtelocentrics (2n = 50). All centromeres are C-band positive. Eight chromosomes have a pericentric C-b

  16. Chromosome painting in plants.

    NARCIS (Netherlands)

    Schubert, I.; Fransz, P.F.; Fuchs, J.; Jong, de J.H.

    2001-01-01

    The current 'state-of-art' as to chromosome painting in plants is reviewed. We define different situations described as painting so far: i) Genomic in situ hybridisation (GISH) with total genomic DNA to distinguish alien chromosomes on the basis of divergent dispersed repeats, ii) 'Chromosomal in si

  17. Zygotes segregate entire parental genomes in distinct blastomere lineages causing cleavage-stage chimerism and mixoploidy.

    Science.gov (United States)

    Destouni, Aspasia; Zamani Esteki, Masoud; Catteeuw, Maaike; Tšuiko, Olga; Dimitriadou, Eftychia; Smits, Katrien; Kurg, Ants; Salumets, Andres; Van Soom, Ann; Voet, Thierry; Vermeesch, Joris R

    2016-05-01

    Dramatic genome dynamics, such as chromosome instability, contribute to the remarkable genomic heterogeneity among the blastomeres comprising a single embryo during human preimplantation development. This heterogeneity, when compatible with life, manifests as constitutional mosaicism, chimerism, and mixoploidy in live-born individuals. Chimerism and mixoploidy are defined by the presence of cell lineages with different parental genomes or different ploidy states in a single individual, respectively. Our knowledge of their mechanistic origin results from indirect observations, often when the cell lineages have been subject to rigorous selective pressure during development. Here, we applied haplarithmisis to infer the haplotypes and the copy number of parental genomes in 116 single blastomeres comprising entire preimplantation bovine embryos (n = 23) following in vitro fertilization. We not only demonstrate that chromosome instability is conserved between bovine and human cleavage embryos, but we also discovered that zygotes can spontaneously segregate entire parental genomes into different cell lineages during the first post-zygotic cleavage division. Parental genome segregation was not exclusively triggered by abnormal fertilizations leading to triploid zygotes, but also normally fertilized zygotes can spontaneously segregate entire parental genomes into different cell lineages during cleavage of the zygote. We coin the term "heterogoneic division" to indicate the events leading to noncanonical zygotic cytokinesis, segregating the parental genomes into distinct cell lineages. Persistence of those cell lines during development is a likely cause of chimerism and mixoploidy in mammals. PMID:27197242

  18. Genetic architecture of male sterility and segregation distortion in Drosophila pseudoobscura Bogota-USA hybrids.

    Science.gov (United States)

    Phadnis, Nitin

    2011-11-01

    Understanding the genetic basis of reproductive isolation between recently diverged species is a central problem in evolutionary genetics. Here, I present analyses of the genetic architecture underlying hybrid male sterility and segregation distortion between the Bogota and USA subspecies of Drosophila pseudoobscura. Previously, a single gene, Overdrive (Ovd), was shown to be necessary but not sufficient for both male sterility and segregation distortion in F(1) hybrids between these subspecies, requiring several interacting partner loci for full manifestation of hybrid phenomena. I map these partner loci separately on the Bogota X chromosome and USA autosomes using a combination of different mapping strategies. I find that hybrid sterility involves a single hybrid incompatibility of at least seven interacting partner genes that includes three large-effect loci. Segregation distortion involves three loci on the Bogota X chromosome and one locus on the autosomes. The genetic bases of hybrid sterility and segregation distortion are at least partially--but not completely--overlapping. My results lay the foundation for fine-mapping experiments to identify the complete set of genes that interact with Overdrive. While individual genes that cause hybrid sterility or inviability have been identified in a few cases, my analysis provides a comprehensive look at the genetic architecture of all components of a hybrid incompatibility underlying F(1) hybrid sterility. Such an analysis would likely be unfeasible for most species pairs due to their divergence time and emphasizes the importance of young species pairs such as the D. pseudoobscura subspecies studied here.

  19. Pericentric inversion of chromosome 12; a three family study

    DEFF Research Database (Denmark)

    Haagerup, A; Hertz, Jens Michael

    1992-01-01

    rate is calculated to be 0.58, which is not significantly different from an expected segregation rate of 0.5. In family 3, an additional inversion of a chromosome 9 has been found in 4 individuals. Our results are discussed in relation to previous findings and with respect to the genetic counselling......A pericentric inversion of chromosome 12 has been followed in three large independently ascertained Danish families. Out of a total number of 52 persons examined, 25 were found to carry the inversion. The breakpoints in all three families were localized to p13 and q13, resulting in more than one...... of families with pericentric inversions....

  20. Gender segregation : from birth to occupation

    OpenAIRE

    Ruiz-Castillo, Javier; Mora, Ricardo

    2003-01-01

    Most of the existing literature studies the gender segregation induced by occupational choices in the employed population. This paper also studies the segregation induced by age/education characteristics and labor market participation decisions in the population consisting of non-students of working age. The gender segregation index used, related to the entropy notion in information theory, is additively decomposable for any partition and it has a commutability property. The em...

  1. Social Exclusion: Residential Segregation in Bolivian Cities

    OpenAIRE

    George Gray-Molina; Wilson Jimenez; Ernesto Perez de Rada

    2002-01-01

    This study analyzes the impact of ethnic-based residential segregation on income and education outcomes in Bolivian cities. Three results stand out in the analysis. First, we find significant and negative segregation effects on income generation in both across-city and intra-city comparisons. Second, we find individual and neighborhood-level interactions between ethnicity and segregation to be significantly and negatively correlated with income and schooling attainment. Finally, we find posit...

  2. The Spatial Context of Residential Segregation

    OpenAIRE

    Roberto, Elizabeth

    2015-01-01

    Residential segregation is defined in a variety of ways to address a common concern: to what extent do social groups reside in separate or distinct places. The spatial pattern of segregation varies widely across cities, and distinct spatial patterns can be generated by different mechanisms and have different consequences for residents and their communities. However, the methods commonly employed to measure segregation ignore how a city is spatially organized. They do not take into account the...

  3. Segregation and Urban Unrest in Sweden

    OpenAIRE

    Malmberg, Bo; Eva, Andersson; Östh, John

    2013-01-01

    In 2009, Sweden experienced a wave of urban unrest concentrated in areas with large foreign-born populations. This episode was seen by many as reflecting a trend towards increased ethnically based residential segregation, in line with scholarly literatures that correlate inequality and rising segregation with increases in unrest or rebellion. In this paper, we analyze the empirical connection between ethnic residential segregation and episodes of urban unrest in Sweden. Unrest is measured by ...

  4. Socio-spatial lifestyles and segregation

    OpenAIRE

    Izhak, Schnell; Yoav, Benjamini

    1999-01-01

    The paper suggests an alternative index for socio-spatial segregation which emphasises agents’ segregation in everyday life. We argue that segregation should be studied for individual agents in respect to the spaces in which they perform their everyday life. The index refers both to the spatial and the social-interactive contexts of seven aspects (home, cluster of neighbouring homes, neighbourhood and city in the spatial context and friends, work and leisure activities in the social context) ...

  5. From particle segregation to the granular clock

    OpenAIRE

    Lambiotte, R.; Salazar, J. M.; Brenig, L.

    2005-01-01

    Recently several authors studied the segregation of particles for a system composed of mono-dispersed inelastic spheres contained in a box divided by a wall in the middle. The system exhibited a symmetry breaking leading to an overpopulation of particles in one side of the box. Here we study the segregation of a mixture of particles composed of inelastic hard spheres and fluidized by a vibrating wall. Our numerical simulations show a rich phenomenology: horizontal segregation and periodic beh...

  6. Chromosome sites play dual roles to establish homologous synapsisduring meiosis in C. elegans

    Energy Technology Data Exchange (ETDEWEB)

    MacQueen, Amy J.; Phillips, Carolyn M.; Bhalla, Needhi; Weiser,Pinky; Villeneuve, Anne M.; Dernburg, Abby F.

    2005-06-05

    required for accurate segregation of homologous chromosomesduring meiosisin C. elegans. We find that these sites play two distinctroles that contribute to proper segregation. Chromosomes lacking PCsusually fail to synapse and also lack a synapsis-independentstabilization activity. The presence of a PC on justone copy of achromosome pair promotes synapsis but does not supportsynapsis-independent pairing stabilization, indicating that thesefunctions are separable. Once initiated, synapsis is highly processive,even between non homologous chromosomes of disparate lengths, elucidatinghow translocations suppress meiotic recombination in C. elegans. Thesefindings suggest a multistep pathway for chromosome synapsis in which PCsimpart selectivity and efficiency through a kinetic proofreadingmechanism. We speculate that concentration of these activities at oneregion per chromosome may have co-evolved with the loss of a pointcentromere to safeguard karyotype stability.

  7. Chiasmata promote monopolar attachment of sister chromatids and their co-segregation toward the proper pole during meiosis I.

    Directory of Open Access Journals (Sweden)

    Yukinobu Hirose

    2011-03-01

    Full Text Available The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis. Chiasmata are essential for the attachment of the homologous chromosomes to opposite spindle poles (bipolar attachment and their subsequent segregation to the opposite poles during meiosis I. However, the overall function of chiasmata during meiosis is not fully understood. Here, we show that chiasmata also play a crucial role in the attachment of sister chromatids to the same spindle pole and in their co-segregation during meiosis I in fission yeast. Analysis of cells lacking chiasmata and the cohesin protector Sgo1 showed that loss of chiasmata causes frequent bipolar attachment of sister chromatids during anaphase. Furthermore, high time-resolution analysis of centromere dynamics in various types of chiasmate and achiasmate cells, including those lacking the DNA replication checkpoint factor Mrc1 or the meiotic centromere protein Moa1, showed the following three outcomes: (i during the pre-anaphase stage, the bipolar attachment of sister chromatids occurs irrespective of chiasma formation; (ii the chiasma contributes to the elimination of the pre-anaphase bipolar attachment; and (iii when the bipolar attachment remains during anaphase, the chiasmata generate a bias toward the proper pole during poleward chromosome pulling that results in appropriate chromosome segregation. Based on these results, we propose that chiasmata play a pivotal role in the selection of proper attachments and provide a backup mechanism that promotes correct chromosome segregation when improper attachments remain during anaphase I.

  8. From particle segregation to the granular clock

    Energy Technology Data Exchange (ETDEWEB)

    Lambiotte, R. [Physique Statistique, Plasmas et Optique Non-lineaire, Universite Libre de Bruxelles, Campus Plaine, Boulevard du Triomphe, Code Postal 231, 1050 Brussels (Belgium)]. E-mail: rlambiot@ulb.ac.be; Salazar, J.M. [Universite De Bougogne-LRRS UMR-5613 CNRS, Faculte des Sciences Mirande, 9 Av. Alain Savary, 21078 Dijon Cedex (France)]. E-mail: jmarcos@u-bourgogne.fr; Brenig, L. [Physique Statistique, Plasmas et Optique Non-lineaire, Universite Libre de Bruxelles, Campus Plaine, Boulevard du Triomphe, Code Postal 231, 1050 Brussels (Belgium)]. E-mail: lbrenig@ulb.ac.be

    2005-08-01

    Recently several authors studied the segregation of particles for a system composed of mono-dispersed inelastic spheres contained in a box divided by a wall in the middle. The system exhibited a symmetry breaking leading to an overpopulation of particles in one side of the box. Here we study the segregation of a mixture of particles composed of inelastic hard spheres and fluidized by a vibrating wall. Our numerical simulations show a rich phenomenology: horizontal segregation and periodic behavior. We also propose an empirical system of ODEs representing the proportion of each type of particles and the segregation flux of particles. These equations reproduce the major features observed by the simulations.

  9. A Social Network Analysis of Occupational Segregation

    DEFF Research Database (Denmark)

    Buhai, Ioan Sebastian; van der Leij, Marco

    We develop a social network model of occupational segregation between different social groups, generated by the existence of positive inbreeding bias among individuals from the same group. If network referrals are important for job search, then expected homophily in the contact network structure...... induces different career choices for individuals from different social groups. This further translates into stable occupational segregation equilibria in the labor market. We derive the conditions for wage and unemployment inequality in the segregation equilibria and characterize first and second best...... social welfare optima. Surprisingly, we find that socially optimal policies involve segregation....

  10. Housing Systems and Ethnic Spatial Segregation

    DEFF Research Database (Denmark)

    Andersen, Hans Skifter; Andersson, Roger; Wessel, Terje;

    Residential spatial segregation is related to housing markets and housing policies. In this paper, ethnic segregation is compared across four Nordic capitals and explanations for the differences are examined by comparing the housing markets and housing policies of the countries. The housing markets...... composition of neighbourhoods. Ethnic segmentation of housing tenures thus contributes to segregation, but the effect is much dependent on how tenures are distributed across space. In one of the cities, the policy of neighbourhood tenure mix has resulted in a relatively low degree of segregation in spite of...

  11. From particle segregation to the granular clock

    International Nuclear Information System (INIS)

    Recently several authors studied the segregation of particles for a system composed of mono-dispersed inelastic spheres contained in a box divided by a wall in the middle. The system exhibited a symmetry breaking leading to an overpopulation of particles in one side of the box. Here we study the segregation of a mixture of particles composed of inelastic hard spheres and fluidized by a vibrating wall. Our numerical simulations show a rich phenomenology: horizontal segregation and periodic behavior. We also propose an empirical system of ODEs representing the proportion of each type of particles and the segregation flux of particles. These equations reproduce the major features observed by the simulations

  12. DIFFUSION AND EQUILIBRIUM SEGREGATION IN GRAIN BOUNDARIES : EFFECTS OF LARGE SEGREGATION

    OpenAIRE

    Bernardini, J.; Cabane, F.

    1985-01-01

    From recent experiments in binary and ternary solid solutions, we discuss the determination of grain boundary diffusion coefficients, some structural aspects of diffusion and segregation and the influence of segregation on impurity diffusion.

  13. Chimpanzee chromosome 12 is homologous to human chromosome 2q

    Energy Technology Data Exchange (ETDEWEB)

    Sun, N. C.; Sun, C. R.Y.; Ho, T.

    1977-01-01

    Most of the 46 human chromosomes find their counterparts in the 48 chimpanzee chromosomes except for chromosome 2 which has been hypothesized to have been derived from a centric fusion of two chimpanzee acrocentric chromosomes. These two chromosomes correspond to the human chromosomes 2p and 2g. This conclusion is based primarily on chromosome banding techniques, and the somatic cell hybridization technique has also been used. (HLW)

  14. Numerical chromosomal instability mediates susceptibility to radiation treatment

    Science.gov (United States)

    Bakhoum, Samuel F.; Kabeche, Lilian; Wood, Matthew D.; Laucius, Christopher D.; Qu, Dian; Laughney, Ashley M.; Reynolds, Gloria E.; Louie, Raymond J.; Phillips, Joanna; Chan, Denise A.; Zaki, Bassem I.; Murnane, John P.; Petritsch, Claudia; Compton, Duane A.

    2015-01-01

    The exquisite sensitivity of mitotic cancer cells to ionizing radiation (IR) underlies an important rationale for the widely used fractionated radiation therapy. However, the mechanism for this cell cycle-dependent vulnerability is unknown. Here we show that treatment with IR leads to mitotic chromosome segregation errors in vivo and long-lasting aneuploidy in tumour-derived cell lines. These mitotic errors generate an abundance of micronuclei that predispose chromosomes to subsequent catastrophic pulverization thereby independently amplifying radiation-induced genome damage. Experimentally suppressing whole-chromosome missegregation reduces downstream chromosomal defects and significantly increases the viability of irradiated mitotic cells. Further, orthotopically transplanted human glioblastoma tumours in which chromosome missegregation rates have been reduced are rendered markedly more resistant to IR, exhibiting diminished markers of cell death in response to treatment. This work identifies a novel mitotic pathway for radiation-induced genome damage, which occurs outside of the primary nucleus and augments chromosomal breaks. This relationship between radiation treatment and whole-chromosome missegregation can be exploited to modulate therapeutic response in a clinically relevant manner. PMID:25606712

  15. Multiple opposing constraints govern chromosome interactions during meiosis.

    Directory of Open Access Journals (Sweden)

    Doris Y Lui

    Full Text Available Homolog pairing and crossing over during meiosis I prophase is required for accurate chromosome segregation to form euploid gametes. The repair of Spo11-induced double-strand breaks (DSB using a homologous chromosome template is a major driver of pairing in many species, including fungi, plants, and mammals. Inappropriate pairing and crossing over at ectopic loci can lead to chromosome rearrangements and aneuploidy. How (or if inappropriate ectopic interactions are disrupted in favor of allelic interactions is not clear. Here we used an in vivo "collision" assay in budding yeast to test the contributions of cohesion and the organization and motion of chromosomes in the nucleus on promoting or antagonizing interactions between allelic and ectopic loci at interstitial chromosome sites. We found that deletion of the cohesin subunit Rec8, but not other chromosome axis proteins (e.g. Red1, Hop1, or Mek1, caused an increase in homolog-nonspecific chromosome interaction, even in the absence of Spo11. This effect was partially suppressed by expression of the mitotic cohesin paralog Scc1/Mdc1, implicating Rec8's role in cohesion rather than axis integrity in preventing nonspecific chromosome interactions. Disruption of telomere-led motion by treating cells with the actin polymerization inhibitor Latrunculin B (Lat B elevated nonspecific collisions in rec8Δ spo11Δ. Next, using a visual homolog-pairing assay, we found that the delay in homolog pairing in mutants defective for telomere-led chromosome motion (ndj1Δ or csm4Δ is enhanced in Lat B-treated cells, implicating actin in more than one process promoting homolog juxtaposition. We suggest that multiple, independent contributions of actin, cohesin, and telomere function are integrated to promote stable homolog-specific interactions and to destabilize weak nonspecific interactions by modulating the elastic spring-like properties of chromosomes.

  16. Alteration of chromosome behavior and synchronization of parental chromosomes after successive generations in Brassica napus x Orychophragmus violaceus hybrids.

    Science.gov (United States)

    Zhao, Zhigang; Ma, Ni; Li, Zaiyun

    2007-02-01

    In an earlier study, the progenies of intergeneric hybrids Brassica napus (2n = 38) x Orychophragmus violaceus (2n = 24) were investigated in successive generations (F1-F4) for the cytological phenomenon of parental genome separation during mitotic and meiotic division. In the present study, inbred lines (F5-F8) derived from 1 such hybrid were characterized for morphology, chromosome pairing behaviour, and genome composition. One F5 plant (2n = 31) with slightly yellow petals and 12:19 and 15:16 segregation ratios in its pollen mother cells (PMCs) produced F6 plants with distinct morphological characteristics and wide variations in fertility and chromosome numbers (2n = 25-38). F7 and F8 lines with distinctive morphology and wide ranges in chromsome numbers were established. In PMCs of F7 plants from 4 F6 plants, 0-12 labelled chromosomes from O. violaceus, which predominantly appeared as bivalents, were identified by genomic in situ hybridization. They behaved synchronously with B. napus chromosomes during meiotic division. The results provide molecular cytogenetic evidence of the inclusion of O. violaceus chromosomes in the original hybrids and the cytology in the hybrids documented earlier. They also show that chromosome behaviour was altered and the parental chromosomes became synchronized after successive generations.

  17. Mechanisms of plasmid segregation: have multicopy plasmids been overlooked?

    Science.gov (United States)

    Million-Weaver, Samuel; Camps, Manel

    2014-09-01

    Plasmids are self-replicating pieces of DNA typically bearing non-essential genes. Given that plasmids represent a metabolic burden to the host, mechanisms ensuring plasmid transmission to daughter cells are critical for their stable maintenance in the population. Here we review these mechanisms, focusing on two active partition strategies common to low-copy plasmids: par systems type I and type II. Both involve three components: an adaptor protein, a motor protein, and a centromere, which is a sequence area in the plasmid that is recognized by the adaptor protein. The centromere-bound adaptor nucleates polymerization of the motor, leading to filament formation, which can pull plasmids apart (par I) or push them towards opposite poles of the cell (par II). No such active partition mechanisms are known to occur in high copy number plasmids. In this case, vertical transmission is generally considered stochastic, due to the random distribution of plasmids in the cytoplasm. We discuss conceptual and experimental lines of evidence questioning the random distribution model and posit the existence of a mechanism for segregation in high copy number plasmids that moves plasmids to cell poles to facilitate transmission to daughter cells. This mechanism would involve chromosomally-encoded proteins and the plasmid origin of replication. Modulation of this proposed mechanism of segregation could provide new ways to enhance plasmid stability in the context of recombinant gene expression, which is limiting for large-scale protein production and for bioremediation.

  18. Orderly Replication and Segregation of the Four Replicons of Burkholderia cenocepacia J2315.

    Science.gov (United States)

    Du, Wen-Li; Dubarry, Nelly; Passot, Fanny M; Kamgoué, Alain; Murray, Heath; Lane, David; Pasta, Franck

    2016-07-01

    Bacterial genomes typically consist of a single chromosome and, optionally, one or more plasmids. But whole-genome sequencing reveals about ten per-cent of them to be multipartite, with additional replicons which by size and indispensability are considered secondary chromosomes. This raises the questions of how their replication and partition is managed without compromising genome stability and of how such genomes arose. Vibrio cholerae, with a 1 Mb replicon in addition to its 3 Mb chromosome, is the only species for which maintenance of a multipartite genome has been investigated. In this study we have explored the more complex genome of Burkholderia cenocepacia (strain J2315). It comprises an extra replicon (c2) of 3.21 Mb, comparable in size to the3.87Mb main chromosome (c1), another extra replicon(c3) of 0.87 Mb and a plasmid of 0.09 Mb. The replication origin of c1 is typically chromosomal and those of c2 and c3 are plasmid-like; all are replicated bidirectionally. Fluorescence microscopy of tagged origins indicates that all initiate replication at mid-cell and segregate towards the cell quarter positions sequentially, c1-c2-p1/c3. c2 segregation is as well-phased with the cell cycle as c1, implying that this plasmid-like origin has become subject to regulation not typical of plasmids; in contrast, c3 segregates more randomly through the cycle. Disruption of individual Par systems by deletion of parAB or by addition of parS sites showed each Par system to govern the positioning of its own replicon only. Inactivation of c1, c2 and c3 Par systems not only reduced growth rate, generated anucleate cells and compromised viability but influenced processes beyond replicon partition, notably regulation of replication, chromosome condensation and cell size determination. In particular, the absence of the c1 ParA protein altered replication of all three chromosomes, suggesting that the partition system of the main chromosome is a major participant in the choreography of

  19. Orderly Replication and Segregation of the Four Replicons of Burkholderia cenocepacia J2315.

    Directory of Open Access Journals (Sweden)

    Wen-Li Du

    2016-07-01

    Full Text Available Bacterial genomes typically consist of a single chromosome and, optionally, one or more plasmids. But whole-genome sequencing reveals about ten per-cent of them to be multipartite, with additional replicons which by size and indispensability are considered secondary chromosomes. This raises the questions of how their replication and partition is managed without compromising genome stability and of how such genomes arose. Vibrio cholerae, with a 1 Mb replicon in addition to its 3 Mb chromosome, is the only species for which maintenance of a multipartite genome has been investigated. In this study we have explored the more complex genome of Burkholderia cenocepacia (strain J2315. It comprises an extra replicon (c2 of 3.21 Mb, comparable in size to the3.87Mb main chromosome (c1, another extra replicon(c3 of 0.87 Mb and a plasmid of 0.09 Mb. The replication origin of c1 is typically chromosomal and those of c2 and c3 are plasmid-like; all are replicated bidirectionally. Fluorescence microscopy of tagged origins indicates that all initiate replication at mid-cell and segregate towards the cell quarter positions sequentially, c1-c2-p1/c3. c2 segregation is as well-phased with the cell cycle as c1, implying that this plasmid-like origin has become subject to regulation not typical of plasmids; in contrast, c3 segregates more randomly through the cycle. Disruption of individual Par systems by deletion of parAB or by addition of parS sites showed each Par system to govern the positioning of its own replicon only. Inactivation of c1, c2 and c3 Par systems not only reduced growth rate, generated anucleate cells and compromised viability but influenced processes beyond replicon partition, notably regulation of replication, chromosome condensation and cell size determination. In particular, the absence of the c1 ParA protein altered replication of all three chromosomes, suggesting that the partition system of the main chromosome is a major participant in the

  20. Embryonic hybrid cells: a powerful tool for studying pluripotency and reprogramming of the differentiated cell chromosomes

    Directory of Open Access Journals (Sweden)

    SEROV OLEG

    2001-01-01

    Full Text Available The properties of embryonic hybrid cells obtained by fusion of embryonic stem (ES or teratocarcinoma (TC cells with differentiated cells are reviewed. Usually, ES-somatic or TC-somatic hybrids retain pluripotent capacity at high levels quite comparable or nearly identical with those of the pluripotent partner. When cultured in vitro, ES-somatic- and TC-somatic hybrid cell clones, as a rule, lose the chromosomes derived from the somatic partner; however, in some clones the autosomes from the ES cell partner were also eliminated, i.e. the parental chromosomes segregated bilaterally in the ES-somatic cell hybrids. This opens up ways for searching correlation between the pluripotent status of the hybrid cells and chromosome segregation patterns and therefore for identifying the particular chromosomes involved in the maintenance of pluripotency. Use of selective medium allows to isolate in vitro the clones of ES-somatic hybrid cells in which "the pluripotent" chromosome can be replaced by "the somatic" counterpart carrying the selectable gene. Unlike the TC-somatic cell hybrids, the ES-somatic hybrids with a near-diploid complement of chromosomes are able to contribute to various tissues of chimeric animals after injection into the blastocoel cavity. Analysis of the chimeric animals showed that the "somatic" chromosome undergoes reprogramming during development. The prospects for the identification of the chromosomes that are involved in the maintenance of pluripotency and its cis- and trans-regulation in the hybrid cell genome are discussed.

  1. Ising, Schelling and Self-Organising Segregation

    CERN Document Server

    Stauffer, D

    2007-01-01

    The similarities between phase separation in physics and residential segregation by preference in the Schelling model of 1971 are reviewed. Also, new computer simulations of asymmetric interactions different from the usual Ising model are presented, showing spontaneous magnetisation (= self-organising segregation) and in one case a sharp phase transition.

  2. Ising, Schelling and self-organising segregation

    Science.gov (United States)

    Stauffer, D.; Solomon, S.

    2007-06-01

    The similarities between phase separation in physics and residential segregation by preference in the Schelling model of 1971 are reviewed. Also, new computer simulations of asymmetric interactions different from the usual Ising model are presented, showing spontaneous magnetisation (=self-organising segregation) and in one case a sharp phase transition.

  3. 17 CFR 32.6 - Segregation.

    Science.gov (United States)

    2010-04-01

    ... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Segregation. 32.6 Section 32.6 Commodity and Securities Exchanges COMMODITY FUTURES TRADING COMMISSION REGULATION OF COMMODITY OPTION TRANSACTIONS § 32.6 Segregation. (a) Any person which accepts money, securities, or property from an...

  4. 49 CFR 176.708 - Segregation distances.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Segregation distances. 176.708 Section 176.708... Requirements for Radioactive Materials § 176.708 Segregation distances. (a) Table IV lists minimum separation... into account any relocation of cargo during the voyage. (e) Any departure from the...

  5. Measuring segregation: an activity space approach

    Science.gov (United States)

    Wong, David W. S.; Shaw, Shih-Lung

    2011-06-01

    While the literature clearly acknowledges that individuals may experience different levels of segregation across their various socio-geographical spaces, most measures of segregation are intended to be used in the residential space. Using spatially aggregated data to evaluate segregation in the residential space has been the norm and thus individual's segregation experiences in other socio-geographical spaces are often de-emphasized or ignored. This paper attempts to provide a more comprehensive approach in evaluating segregation beyond the residential space. The entire activity spaces of individuals are taken into account with individuals serving as the building blocks of the analysis. The measurement principle is based upon the exposure dimension of segregation. The proposed measure reflects the exposure of individuals of a referenced group in a neighborhood to the populations of other groups that are found within the activity spaces of individuals in the referenced group. Using the travel diary data collected from the tri-county area in southeast Florida and the imputed racial-ethnic data, this paper demonstrates how the proposed segregation measurement approach goes beyond just measuring population distribution patterns in the residential space and can provide a more comprehensive evaluation of segregation by considering various socio-geographical spaces.

  6. Residential Segregation: Challenge to White America.

    Science.gov (United States)

    Denton, Nancy A.

    1994-01-01

    Examines the problem of residential segregation and demonstrates that it is a problem of social structure. The author contends that residential segregation has affirmed the continued subordination of blacks in American society over the past 50 years. New leadership in the Department of Housing and Urban Development is viewed as a positive…

  7. Measuring segregation: an activity space approach.

    Science.gov (United States)

    Wong, David W S; Shaw, Shih-Lung

    2011-06-01

    While the literature clearly acknowledges that individuals may experience different levels of segregation across their various socio-geographical spaces, most measures of segregation are intended to be used in the residential space. Using spatially aggregated data to evaluate segregation in the residential space has been the norm and thus individual's segregation experiences in other socio-geographical spaces are often de-emphasized or ignored. This paper attempts to provide a more comprehensive approach in evaluating segregation beyond the residential space. The entire activity spaces of individuals are taken into account with individuals serving as the building blocks of the analysis. The measurement principle is based upon the exposure dimension of segregation. The proposed measure reflects the exposure of individuals of a referenced group in a neighborhood to the populations of other groups that are found within the activity spaces of individuals in the referenced group. Using the travel diary data collected from the tri-county area in southeast Florida and the imputed racial-ethnic data, this paper demonstrates how the proposed segregation measurement approach goes beyond just measuring population distribution patterns in the residential space and can provide a more comprehensive evaluation of segregation by considering various socio-geographical spaces.

  8. Losing Ground: School Segregation in Massachuestts

    Science.gov (United States)

    Ayscue, Jennifer B.; Greenberg, Alyssa

    2013-01-01

    Though once a leader in school integration, Massachusetts has regressed over the last two decades as its students of color have experienced intensifying school segregation. This report investigates trends in school segregation in Massachusetts by examining concentration, exposure, and evenness measures by both race and class. First, the report…

  9. Occupational Segregation by Sex: Trends and Prospects.

    Science.gov (United States)

    Blau, Francine D.; Hendricks, Wallace E.

    1979-01-01

    Investigates postwar trends in occupational segregation. Finds segregation increased slightly between 1950-60 as predominantly female clerical/professional jobs increased. Occupation mix changes (1960-70) were neutral in impact, but male inflow into female professions and female inflow into male sales/clerical jobs produced modest segregation…

  10. PARTICLE SEGREGATION IN FLUIDIZED BINARY-MIXTURES

    NARCIS (Netherlands)

    HOFFMANN, AC; JANSSEN, LPBM

    1993-01-01

    The particle segregation in fluidised beds consisting of different types of binary mixtures is shown to be governed by the same particle transport processes. The segregation behaviour of both ''different-density mixtures'' and ''equal-density mixtures'', two types of system which until now largely h

  11. Phosphorylation of chromosome core components may serve as axis marks for the status of chromosomal events during mammalian meiosis.

    Directory of Open Access Journals (Sweden)

    Tomoyuki Fukuda

    2012-02-01

    Full Text Available Meiotic recombination and chromosome synapsis between homologous chromosomes are essential for proper chromosome segregation at the first meiotic division. While recombination and synapsis, as well as checkpoints that monitor these two events, take place in the context of a prophase I-specific axial chromosome structure, it remains unclear how chromosome axis components contribute to these processes. We show here that many protein components of the meiotic chromosome axis, including SYCP2, SYCP3, HORMAD1, HORMAD2, SMC3, STAG3, and REC8, become post-translationally modified by phosphorylation during the prophase I stage. We found that HORMAD1 and SMC3 are phosphorylated at a consensus site for the ATM/ATR checkpoint kinase and that the phosphorylated forms of HORMAD1 and SMC3 localize preferentially to unsynapsed chromosomal regions where synapsis has not yet occurred, but not to synapsed or desynapsed regions. We investigated the genetic requirements for the phosphorylation events and revealed that the phosphorylation levels of HORMAD1, HORMAD2, and SMC3 are dramatically reduced in the absence of initiation of meiotic recombination, whereas BRCA1 and SYCP3 are required for normal levels of phosphorylation of HORMAD1 and HORMAD2, but not of SMC3. Interestingly, reduced HORMAD1 and HORMAD2 phosphorylation is associated with impaired targeting of the MSUC (meiotic silencing of unsynapsed chromatin machinery to unsynapsed chromosomes, suggesting that these post-translational events contribute to the regulation of the synapsis surveillance system. We propose that modifications of chromosome axis components serve as signals that facilitate chromosomal events including recombination, checkpoint control, transcription, and synapsis regulation.

  12. UNUSUAL SEGREGATION BEHAVIOR OF BORON AND ITS EFFECT ON SEGREGATION OF SULFUR IN NICKEL

    OpenAIRE

    Ladna, B.; Birnbaum, H

    1988-01-01

    The co-segregation of B and S to the surface and grain boundaries of Ni was studied by SAES and SIMS. B showed an unusual segregation behavior wich resulted in the precipitation of Ni3B in the near surface layer and a continuous monolayer type B segregation at the grain boundary. The S segregation was not influenced by the presence of B and resulted in a uniform monolayer surface and grain boundary coverage. Analysis of hydrogen charged samples fractured in situ suggests that B segregated to ...

  13. The Precarious Prokaryotic Chromosome

    OpenAIRE

    Kuzminov, Andrei

    2014-01-01

    Evolutionary selection for optimal genome preservation, replication, and expression should yield similar chromosome organizations in any type of cells. And yet, the chromosome organization is surprisingly different between eukaryotes and prokaryotes. The nuclear versus cytoplasmic accommodation of genetic material accounts for the distinct eukaryotic and prokaryotic modes of genome evolution, but it falls short of explaining the differences in the chromosome organization. I propose that the t...

  14. On the Segregation of Dark Matter Substructure

    CERN Document Server

    Bosch, Frank C van den; Campbell, Duncan; Behroozi, Peter

    2015-01-01

    We present the first comprehensive analysis of the segregation of dark matter subhaloes in their host haloes. Using numerical simulations, we examine the segregation of twelve different subhalo properties with respect to both orbital energy and halo-centric radius (in real space as well as in projection). Subhaloes are strongly segregated by accretion redshift, which is an outcome of the inside-out assembly of their host haloes. Since subhaloes that were accreted earlier have experienced more tidal stripping, subhaloes that have lost a larger fraction of their mass at infall are on more bound orbits. Subhaloes are also strongly segregated in their masses and maximum circular velocities at accretion. We demonstrate that part of this segregation is already imprinted in the infall conditions. For massive subhaloes it is subsequently boosted by dynamical friction, but only during their first radial orbit. The impact of these two effects is counterbalanced, though, by the fact that subhaloes with larger accretion ...

  15. The Spatial Context of Residential Segregation

    CERN Document Server

    Roberto, Elizabeth

    2015-01-01

    Scholars have engaged in a longstanding debate about how best to measure residential segregation, and scores of indexes have been developed in response. However, the methods commonly employed are aspatial -- they summarize the characteristics of segregation patterns, such as concentration or clustering, but ignore their spatial features, such as how neighborhoods are spatially arranged. As a consequence, many studies find the same level of segregation whether a city has a patchwork of racial and ethnic enclaves, or is divided into large areas with little or no diversity. New methods have been developed to capture the spatial proximity of neighborhoods and the geographic scale of clustering. However, they lack a realistic measure of distance and do not accurately represent how segregation varies within cities. In this paper, I introduce a new method for studying the spatial context of residential segregation. I measure the distance between locations along city roads rather than in a straight line. Road distanc...

  16. Ring chromosome 13

    DEFF Research Database (Denmark)

    Brandt, C A; Hertz, Jens Michael; Petersen, M B;

    1992-01-01

    A stillborn male child with anencephaly and multiple malformations was found to have the karyotype 46,XY,r(13) (p11q21.1). The breakpoint at 13q21.1, determined by high resolution banding, is the most proximal breakpoint ever reported in patients with ring chromosome 13. In situ hybridisation...... with the probe L1.26 confirmed the derivation from chromosome 13 and DNA polymorphism analysis showed maternal origin of the ring chromosome. Our results, together with a review of previous reports of cases with ring chromosome 13 with identified breakpoints, could neither support the theory of distinct clinical...

  17. Genetic Segregation and Genomic Hybridization Patterns Support an Allotetraploid Structure and Disomic Inheritance for Salix Species

    Directory of Open Access Journals (Sweden)

    Gianni Barcaccia

    2014-09-01

    Full Text Available The Salix alba L. (white willow—Salix fragilis L. (crack willow complex includes closely related polyploid species, mainly tetraploid (2n = 4x = 76, which are dioecious and hence obligate allogamous. Because little is known about the genome constitution and chromosome behavior of these pure willow trees, genetic analysis of their naturally occurring interspecific polyploid hybrids is still very difficult. A two-way pseudo-testcross strategy was exploited using single-dose AFLP markers in order to assess the main inheritance patterns of tetraploid biotypes (disomy vs. tetrasomy in segregating populations stemmed from S. alba × S. fragilis crosses and reciprocals. In addition, a genomic in situ hybridization (GISH technology was implemented in willow to shed some light on the genome structure of S. alba and S. fragilis species, and their hybrids (allopolyploidy vs. autopolyploidy. The frequency of S. alba-specific molecular markers was almost double compared to that of S. fragilis-specific ones, suggesting the phylogenetic hypothesis of S. fragilis as derivative species from S. alba-like progenitors. Cytogenetic observations at pro-metaphase revealed about half of the chromosome complements being less contracted than the remaining ones, supporting an allopolyploid origin of both S. alba and S. fragilis. Both genetic segregation and genomic hybridization data are consistent with an allotetraploid nature of the Salix species. In particular, the vast majority of the AFLP markers were inherited according to disomic patterns in S. alba × S. fragilis populations and reciprocals. Moreover, in all S. alba against S. fragilis hybridizations and reciprocals, GISH signals were observed only on the contracted chromosomes whereas the non-contracted chromosomes were never hybridized. In conclusion, half of the chromosomes of the pure species S. alba and S. fragilis are closely related and they could share a common diploid ancestor, while the rest of

  18. Simple queueing approach to segregation dynamics in Schelling model

    OpenAIRE

    Sobkowicz, Pawel

    2007-01-01

    A simple queueing approach for segregation of agents in modified one dimensional Schelling segregation model is presented. The goal is to arrive at simple formula for the number of unhappy agents remaining after the segregation.

  19. Referral Hiring and Gender Segregation in the Workplace

    OpenAIRE

    Troy Tassier

    2008-01-01

    Segregation by type of work or discrimination are two common explanations for gender segregation in the workplace. A third, gender segregation due to referral hiring through segregated social networks, is less well explored. In this paper, I use an agent-based model of referral hiring to demonstrate that it could create high levels of gender segregation near those observed in data. But the model cannot account for all of the segregation observed. Eastern Economic Journal (2008) 34, 429–440. d...

  20. Chromosomal mosaicism : underlying mechanisms and consequences for early human embryo development

    NARCIS (Netherlands)

    da Avó Ribeiro dos Santos, M.

    2013-01-01

    In humans, reproduction is considered a relatively inefficient process, when compared with other mammalian species and the chance of achieving a spontaneous pregnancy after timed intercourse is at the most 20-30%. Chromosome segregation errors are a well-known inherent feature of cell division in hu

  1. Cosegregation of hypertrophic cardiomyopathy and a fragile site on chromosome 16 in a large Italian family.

    OpenAIRE

    M. Ferraro; Scarton, G; Ambrosini, M

    1990-01-01

    We studied the karyotypes of 10 members of a family in whom hypertrophic cardiomyopathy is segregating as an autosomal dominant trait. In all those affected by the disease, a fragile site on the long arm of chromosome 16 was found, expressed with different frequencies, but the unaffected family members did not show this trait.

  2. Cohesin SMC1 beta is required for meiotic chromosome dynamics, sister chromatid cohesion and DNA recombination

    NARCIS (Netherlands)

    Revenkova, E.; Eijpe, M.; Heyting, C.; Hodges, C.A.; Hunt, P.A.; Liebe, B.; Scherthan, H.; Jessberger, R.

    2004-01-01

    Sister chromatid cohesion ensures the faithful segregation of chromosomes in mitosis and in both meiotic divisions1, 2, 3, 4. Meiosis-specific components of the cohesin complex, including the recently described SMC1 isoform SMC15, were suggested to be required for meiotic sister chromatid cohesion a

  3. Modeling density segregation in granular flow

    Science.gov (United States)

    Xiao, Hongyi; Lueptow, Richard; Umbanhowar, Paul

    2015-11-01

    A recently developed continuum-based model accurately predicts segregation in flows of granular mixtures varying in particle size by considering the interplay of advection, diffusion and segregation. In this research, we extend the domain of the model to include density driven segregation. Discrete Element Method (DEM) simulations of density bidisperse flows of mono-sized particles in a quasi-2D bounded heap were performed to determine the dependence of the density driven segregation velocity on local shear rate, particle concentration, and a segregation length which scales with the particle size and the logarithm of the density ratio. With these inputs, the model yields theoretical predictions of density segregation patterns that quantitatively match the DEM simulations over a range of density ratios (1.11-3.33) and flow rates (19.2-113.6 cm3/s). Matching experiments with various combinations of glass, steel and ceramic particles were also performed which reproduced the segregation patterns obtained in both the simulations and the theory.

  4. Occurrence of differential meiotic associations and additional chromosomes in the embryo-sac mother cells of Allium roylei Stearn

    Indian Academy of Sciences (India)

    Geeta Sharma; Ravinder N. Gohil

    2011-04-01

    A small population of complex translocation heterozygote plants of Allium roylei from the Bani region of Jammu Province was studied for meiosis in the female track. This study resulted in identification of two variants, having embryo-sac mother cells (EMCs) with more than 16 chromosomes. EMCs of the remaining plants invariably had diploid $(2n = 16)$ chromosome complement. Female meiosis, in general, was found to be abnormal, with nearly 23% and 11% chromosomes associating as quadrivalents or trivalents at prophase I and at metaphase I, respectively. This was followed by irregular segregation of chromosomes at anaphase I. Amongst the variants; one had 38% EMCs with eight bivalents plus two small sized chromosomes. Their small size, dispensable nature and tendency to affect the pairing behaviour of normal complement are some of the features that latter chromosomes share with the B chromosomes. Seventeen to nineteen chromosomes were observed in 35% EMCs of other variant; the remaining cells had 16 chromosomes. Chromosomal behaviour in both kind of cells (euploid and aneuploid) was more or less similar. Unlike female meiocytes, male meiocytes analysed earlier of this strain always had 16 chromosomes which paired to form extremely complex associations involving 3–16 chromosomes. The most likely cause of this asynchrony with regards to number of chromosomes involved in multivalent formation seems to be interaction of genes controlling chiasma formation with the different physiological conditions of male and female meiocytes.

  5. Electochemical detection of chromosome translocation

    DEFF Research Database (Denmark)

    Kwasny, Dorota; Dimaki, Maria; Silahtaroglu, Asli;

    2014-01-01

    Cytogenetics is a study of the cell structure with a main focus on chromosomes content and their structure. Chromosome abnormalities, such as translocations may cause various genetic disorders and heametological malignancies. Chromosome translocations are structural rearrangements of two chromoso...

  6. Topoisomerase IIα in chromosome instability and personalized cancer therapy.

    Science.gov (United States)

    Chen, T; Sun, Y; Ji, P; Kopetz, S; Zhang, W

    2015-07-30

    Genome instability is a hallmark of cancer cells. Chromosome instability (CIN), which is often mutually exclusive from hypermutation genotypes, represents a distinct subtype of genome instability. Hypermutations in cancer cells are due to defects in DNA repair genes, but the cause of CIN is still elusive. However, because of the extensive chromosomal abnormalities associated with CIN, its cause is likely a defect in a network of genes that regulate mitotic checkpoints and chromosomal organization and segregation. Emerging evidence has shown that the chromosomal decatenation checkpoint, which is critical for chromatin untangling and packing during genetic material duplication, is defective in cancer cells with CIN. The decatenation checkpoint is known to be regulated by a family of enzymes called topoisomerases. Among them, the gene encoding topoisomerase IIα (TOP2A) is commonly altered at both gene copy number and gene expression level in cancer cells. Thus, abnormal alterations of TOP2A, its interacting proteins, and its modifications may have a critical role in CIN in human cancers. Clinically, a large arsenal of topoisomerase inhibitors has been used to suppress DNA replication in cancer. However, they often lead to the secondary development of leukemia because of their effect on the chromosomal decatenation checkpoint. Therefore, topoisomerase drugs must be used judiciously and administered on an individual basis. In this review, we highlight the biological function of TOP2A in chromosome segregation and the mechanisms that regulate this enzyme's expression and activity. We also review the roles of TOP2A and related proteins in human cancers, and raise a perspective for how to target TOP2A in personalized cancer therapy. PMID:25328138

  7. Mitotic Protein CSPP1 Interacts with CENP-H Protein to Coordinate Accurate Chromosome Oscillation in Mitosis.

    Science.gov (United States)

    Zhu, Lijuan; Wang, Zhikai; Wang, Wenwen; Wang, Chunli; Hua, Shasha; Su, Zeqi; Brako, Larry; Garcia-Barrio, Minerva; Ye, Mingliang; Wei, Xuan; Zou, Hanfa; Ding, Xia; Liu, Lifang; Liu, Xing; Yao, Xuebiao

    2015-11-01

    Mitotic chromosome segregation is orchestrated by the dynamic interaction of spindle microtubules with the kinetochores. During chromosome alignment, kinetochore-bound microtubules undergo dynamic cycles between growth and shrinkage, leading to an oscillatory movement of chromosomes along the spindle axis. Although kinetochore protein CENP-H serves as a molecular control of kinetochore-microtubule dynamics, the mechanistic link between CENP-H and kinetochore microtubules (kMT) has remained less characterized. Here, we show that CSPP1 is a kinetochore protein essential for accurate chromosome movements in mitosis. CSPP1 binds to CENP-H in vitro and in vivo. Suppression of CSPP1 perturbs proper mitotic progression and compromises the satisfaction of spindle assembly checkpoint. In addition, chromosome oscillation is greatly attenuated in CSPP1-depleted cells, similar to what was observed in the CENP-H-depleted cells. Importantly, CSPP1 depletion enhances velocity of kinetochore movement, and overexpression of CSPP1 decreases the speed, suggesting that CSPP1 promotes kMT stability during cell division. Specific perturbation of CENP-H/CSPP1 interaction using a membrane-permeable competing peptide resulted in a transient mitotic arrest and chromosome segregation defect. Based on these findings, we propose that CSPP1 cooperates with CENP-H on kinetochores to serve as a novel regulator of kMT dynamics for accurate chromosome segregation.

  8. Chromosome synapsis and recombination in simple and complex chromosomal heterozygotes of tuco-tuco (Ctenomys talarum: Rodentia: Ctenomyidae).

    Science.gov (United States)

    Basheva, Ekaterina A; Torgasheva, Anna A; Gomez Fernandez, Maria Jimena; Boston, Emma; Mirol, Patricia; Borodin, Pavel M

    2014-09-01

    The chromosomal speciation hypothesis suggests that irregularities in synapsis, recombination, and segregation in heterozygotes for chromosome rearrangements may restrict gene flow between karyotypically distinct populations and promote speciation. Ctenomys talarum is a South American subterranean rodent inhabiting the coastal regions of Argentina, whose populations polymorphic for Robertsonian and tandem translocations seem to have a very restricted gene flow. To test if chromosomal differences are involved in isolation among its populations, we examined chromosome pairing, recombination, and meiotic silencing of unsynapsed chromatin in male meiosis of simple and complex translocation heterozygotes using immunolocalization of the MLH1 marking mature recombination nodules and phosphorylated histone γH2A.X marking unrepaired double-strand breaks. We observed small asynaptic areas labeled by γH2A.X in pericentromeric regions of the chromosomes involved in the trivalents and quadrivalents. We also observed a decrease of recombination frequency and a distalization of the crossover distribution in the heterozygotes and metacentric homozygotes compared to acrocentric homozygotes. We suggest that the asynapsis of the pericentromeric regions are unlikely to induce germ cell death and decrease fertility of the heterozygotes; however, suppressed recombination in pericentromeric areas of the multivalents may reduce gene flow between chromosomally different populations of the Talas tuco-tuco. PMID:24924853

  9. Veil: A Wall of Segregation

    Directory of Open Access Journals (Sweden)

    Tayebeh Nowrouzi

    2015-08-01

    Full Text Available Moving behind the confines of the race has been the continuous efforts of African-Americans so as to reveal and confirm their true humanity and abilities to white race as well as their own race. African-Americans, Dubois posited, are shut out of the white America, inhabiting behind a vast veil which creates a deep division between the races. Veil is made of the fabric of racism interwoven thread by thread and imposed by white world. It is thrown discourteously and forcibly to the African-Americans whom their distorted images are imposed on them and their true humanity and identity are hidden behind the veil. This study overtakes to present how Loraine Hansberry, in her first and the most outstanding drama, A Raisin in the Sun examines the world within the veil. She demonstrated that Duboisian metaphoric veil is operating in the racist American society so that not only African-Americans are segregated physically and psychologically from the rest of the world but also are inflicted with obscurity of vision that are neither able to see themselves clearly nor be seen truly. On the other hand, it presents how the veil provides blacks with the second sight to observe and comprehend the racist nature of whites which is hidden and incomprehensible for them.

  10. Ki-67 acts as a biological surfactant to disperse mitotic chromosomes.

    Science.gov (United States)

    Cuylen, Sara; Blaukopf, Claudia; Politi, Antonio Z; Müller-Reichert, Thomas; Neumann, Beate; Poser, Ina; Ellenberg, Jan; Hyman, Anthony A; Gerlich, Daniel W

    2016-07-14

    Eukaryotic genomes are partitioned into chromosomes that form compact and spatially well-separated mechanical bodies during mitosis. This enables chromosomes to move independently of each other for segregation of precisely one copy of the genome to each of the nascent daughter cells. Despite insights into the spatial organization of mitotic chromosomes and the discovery of proteins at the chromosome surface, the molecular and biophysical bases of mitotic chromosome structural individuality have remained unclear. Here we report that the proliferation marker protein Ki-67 (encoded by the MKI67 gene), a component of the mitotic chromosome periphery, prevents chromosomes from collapsing into a single chromatin mass after nuclear envelope disassembly, thus enabling independent chromosome motility and efficient interactions with the mitotic spindle. The chromosome separation function of human Ki-67 is not confined within a specific protein domain, but correlates with size and net charge of truncation mutants that apparently lack secondary structure. This suggests that Ki-67 forms a steric and electrostatic charge barrier, similar to surface-active agents (surfactants) that disperse particles or phase-separated liquid droplets in solvents. Fluorescence correlation spectroscopy showed a high surface density of Ki-67 and dual-colour labelling of both protein termini revealed an extended molecular conformation, indicating brush-like arrangements that are characteristic of polymeric surfactants. Our study thus elucidates a biomechanical role of the mitotic chromosome periphery in mammalian cells and suggests that natural proteins can function as surfactants in intracellular compartmentalization. PMID:27362226

  11. Ki-67 acts as a biological surfactant to disperse mitotic chromosomes.

    Science.gov (United States)

    Cuylen, Sara; Blaukopf, Claudia; Politi, Antonio Z; Müller-Reichert, Thomas; Neumann, Beate; Poser, Ina; Ellenberg, Jan; Hyman, Anthony A; Gerlich, Daniel W

    2016-06-29

    Eukaryotic genomes are partitioned into chromosomes that form compact and spatially well-separated mechanical bodies during mitosis. This enables chromosomes to move independently of each other for segregation of precisely one copy of the genome to each of the nascent daughter cells. Despite insights into the spatial organization of mitotic chromosomes and the discovery of proteins at the chromosome surface, the molecular and biophysical bases of mitotic chromosome structural individuality have remained unclear. Here we report that the proliferation marker protein Ki-67 (encoded by the MKI67 gene), a component of the mitotic chromosome periphery, prevents chromosomes from collapsing into a single chromatin mass after nuclear envelope disassembly, thus enabling independent chromosome motility and efficient interactions with the mitotic spindle. The chromosome separation function of human Ki-67 is not confined within a specific protein domain, but correlates with size and net charge of truncation mutants that apparently lack secondary structure. This suggests that Ki-67 forms a steric and electrostatic charge barrier, similar to surface-active agents (surfactants) that disperse particles or phase-separated liquid droplets in solvents. Fluorescence correlation spectroscopy showed a high surface density of Ki-67 and dual-colour labelling of both protein termini revealed an extended molecular conformation, indicating brush-like arrangements that are characteristic of polymeric surfactants. Our study thus elucidates a biomechanical role of the mitotic chromosome periphery in mammalian cells and suggests that natural proteins can function as surfactants in intracellular compartmentalization.

  12. Nucleoporin translocated promoter region (Tpr) associates with dynein complex, preventing chromosome lagging formation during mitosis.

    Science.gov (United States)

    Nakano, Hiroshi; Funasaka, Tatsuyoshi; Hashizume, Chieko; Wong, Richard W

    2010-04-01

    Gain or loss of whole chromosomes is often observed in cancer cells and is thought to be due to aberrant chromosome segregation during mitosis. Proper chromosome segregation depends on a faithful interaction between spindle microtubules and kinetochores. Several components of the nuclear pore complex/nucleoporins play critical roles in orchestrating the rapid remodeling events that occur during mitosis. Our recent studies revealed that the nucleoporin, Rae1, plays critical roles in maintaining spindle bipolarity. Here, we show association of another nucleoporin, termed Tpr (translocated promoter region), with the molecular motors dynein and dynactin, which both orchestrate with the spindle checkpoints Mad1 and Mad2 during cell division. Overexpression of Tpr enhanced multinucleated cell formation. RNA interference-mediated knockdown of Tpr caused a severe lagging chromosome phenotype and disrupted spindle checkpoint proteins expression and localization. Next, we performed a series of rescue and dominant negative experiments to confirm that Tpr orchestrates proper chromosome segregation through interaction with dynein light chain. Our data indicate that Tpr functions as a spatial and temporal regulator of spindle checkpoints, ensuring the efficient recruitment of checkpoint proteins to the molecular motor dynein to promote proper anaphase formation.

  13. The Distribution of Segregation in Atlanta

    Science.gov (United States)

    Meade, Anthony

    1972-01-01

    A prediction from ecological theory relating the distribution of residential segregation between inner and outer zones of a metropolitan area to conditions of population growth, expansion, etc. was tested using 1960 data on the Atlanta standard metropolitan statistical area. (JM)

  14. Residential Segregation in Southern Cities: 1970

    Science.gov (United States)

    And Others; Roof, Wade Clark

    1976-01-01

    Based on an analysis of the age, size, percent black, and occupational income differential in 32 southern cities, the findings show that age is still the strongest predictor of residential segregation. (Author)

  15. Demographic processes and ethnic residential segregation

    Directory of Open Access Journals (Sweden)

    Itzhak Omer

    1999-01-01

    Full Text Available This paper examines the involvement of demographic processes in the residential segregation of ethnic groups in an urban area. For this purpose, a two-part methodology has been employed. The first part comprises a conceptual framework which uses the concept of time–space resources as an analytical tool to clarify the structural constraints embedded in the changes in ethnic residential distribution. The second part comprises a simulation model of ethnic residential segregation. The model, which fits into the category of agent-based simulation models, serves as a tool for heuristic study. The methodology has been applied to examine the implications of fluctuations in ethnic group diffusion and the residential mobility rate on the majority–minority residential segregation, and on the internal ethnic segregation within the minority group.

  16. Phenotypic variability in a seven-generation Swedish family segregating autosomal dominant hearing impairment due to a novel EYA4 frameshift mutation

    DEFF Research Database (Denmark)

    Frykholm, Carina; Klar, Joakim; Arnesson, Hanna;

    2015-01-01

    Linkage to an interval overlapping the DFNA10 locus on chromosome 6q22-23 was found through genome wide linkage analysis in a seven-generation Swedish family segregating postlingual, autosomal dominant nonsyndromic sensorineural hearing impairment. A novel heterozygous frame-shift mutation (c.579...

  17. The double par locus of virulence factor pB171: DNA segregation is correlated with oscillation of ParA

    DEFF Research Database (Denmark)

    Ebersbach, G; Gerdes, K; Charbon, Gitte Ebersbach

    2001-01-01

    Prokaryotic plasmids and chromosomes encode partitioning (par) loci that segregate DNA to daughter cells before cell division. Recent database analyses showed that almost all known par loci encode an ATPase and a DNA-binding protein, and one or more cis-acting regions where the proteins act. All...

  18. Gender Differences in the Effect of Residential Segregation on Workplace Segregation among Newly Arrived Immigrants

    OpenAIRE

    Tammaru, Tiit; Strömgren, Magnus; van Ham, Maarten; Danzer, Alexander M.

    2015-01-01

    Contemporary cities are becoming more and more diverse in population as a result of immigration. Research also shows that within cities residential neighborhoods are becoming ethnically more diverse, but that residential segregation has remained persistently high. High levels of segregation are often seen as negative, preventing integration of immigrants in their host society and having a negative impact on people's lives. Segregation research often focuses on residential neighborhoods, but i...

  19. Modeling size segregation of bidisperse granular flow: the roles of segregation, advection, and diffusion

    OpenAIRE

    Fan, Yi; Schlick, Conor; Isner, Austin; Ottino, Julio; Umbanhowar, Paul; Richard, Lueptow

    2014-01-01

    Segregation of granular materials composed of different-sized particles has important repercussions in various industrial processes and natural phenomena, but predicting size segregation remains a challenging problem. To address this problem, we have developed a theoretical model that captures the interplay between advection, segregation, and diffusion in size bidisperse granular materials. The fluxes associated with these three driving factors depend on the underlying kinematics, whose chara...

  20. Sequential cloning of chromosomes

    Energy Technology Data Exchange (ETDEWEB)

    Lacks, S.A.

    1991-12-31

    A method for sequential cloning of chromosomal DNA and chromosomal DNA cloned by this method are disclosed. The method includes the selection of a target organism having a segment of chromosomal DNA to be sequentially cloned. A first DNA segment, having a first restriction enzyme site on either side. homologous to the chromosomal DNA to be sequentially cloned is isolated. A first vector product is formed by ligating the homologous segment into a suitably designed vector. The first vector product is circularly integrated into the target organism`s chromosomal DNA. The resulting integrated chromosomal DNA segment includes the homologous DNA segment at either end of the integrated vector segment. The integrated chromosomal DNA is cleaved with a second restriction enzyme and ligated to form a vector-containing plasmid, which is replicated in a host organism. The replicated plasmid is then cleaved with the first restriction enzyme. Next, a DNA segment containing the vector and a segment of DNA homologous to a distal portion of the previously isolated DNA segment is isolated. This segment is then ligated to form a plasmid which is replicated within a suitable host. This plasmid is then circularly integrated into the target chromosomal DNA. The chromosomal DNA containing the circularly integrated vector is treated with a third, retrorestriction enzyme. The cleaved DNA is ligated to give a plasmid that is used to transform a host permissive for replication of its vector. The sequential cloning process continues by repeated cycles of circular integration and excision. The excision is carried out alternately with the second and third enzymes.

  1. Segregation and Labor Discrimination in Cities

    OpenAIRE

    Gannon, Frédéric; Zenou, Yves

    1997-01-01

    The aim of this paper is to analyze segregation and labor discrimination in a monocentric city. We first show that, if some categories are systematically discriminated in the labor market (such as blacks, young people, long-rum unemployed...), they will also be spatially segregated at the vicinity of the CBD. Second, we perform comparative statics to examine how urban configuration is modified in equilibrium by changes in labor market characteristics. Finally, we contemplate two policies that...

  2. Demographic processes and ethnic residential segregation

    OpenAIRE

    Itzhak Omer

    1999-01-01

    This paper examines the involvement of demographic processes in the residential segregation of ethnic groups in an urban area. For this purpose, a two-part methodology has been employed. The first part comprises a conceptual framework which uses the concept of time–space resources as an analytical tool to clarify the structural constraints embedded in the changes in ethnic residential distribution. The second part comprises a simulation model of ethnic residential segregation. The model, whic...

  3. Decentralization as a Cause of Spatial Segregation

    OpenAIRE

    Jasarovic Ema Alihodzic; Komatina Dragan; Zaric Sanja Paunovic

    2016-01-01

    City represents an incomplete dynamic process prone to the expansion with a causal link between urban expansion and socio-spatial segregation. The socio-spatial distribution in the city is mostly related to the increased social polarization and inequality. There is a clear connection between divided society and divided city: if society is divided, urban space must be divided. It is the question of the relations between the social inequalities on one hand, and spatial segregation on the other....

  4. A physical approach to segregation and folding of the Caulobacter crescentus genome.

    Science.gov (United States)

    Dame, Remus T; Tark-Dame, Mariliis; Schiessel, Helmut

    2011-12-01

    Bacterial genomes are functionally organized. This organization is dynamic and globally changing throughout the cell cycle. Upon initiation of replication of the chromosome, the two origins segregate and move towards their new location taking along the newly replicated genome. Caulobacter crescentus employs a dedicated active partitioning (Par) system to move one copy of the parS centromere to the distal pole, while the other stays at the stalked pole. In this issue of Molecular Microbiology, Hong and McAdams describe studies on the speed of segregation of parS and regions up to 150 kb away. They show clear differences in segregation rates between parS and 50 kb flanking regions versus regions further away. To assess segregation rates the authors track fluorescent markers during movement using time-lapse microscopy. The relation between genomic and physical distance of pairs of markers reflects how the genome is folded. This relation permits testing experimental data against models from polymer physics. Such models are helpful in understanding principles of genome folding. Although long used in studies on eukaryotes, this approach has rarely been applied to bacteria. Finally, the authors give the first direct evidence for a role of the bacterial chromatin protein HU in folding the genome in vivo.

  5. Chromosome numbers and meiotic analysis in the pre-breeding of Brachiaria decumbens (Poaceae)

    Indian Academy of Sciences (India)

    Gléia Cristina Laverde Ricci; Alice Maria De Souza-Kaneshima; Mariana Ferrari Felismino; Andrea Beatriz Mendes-Bonato; Maria Suely Pagliarini; Cacilda Borges Do Valle

    2011-08-01

    A total of 44 accessions of Brachiaria decumbens were analysed for chromosome count and meiotic behaviour in order to identify potential progenitors for crosses. Among them, 15 accessions presented $2n = 18$; 27 accessions, $2n = 36$; and 2 accessions, $2n = 45$ chromosomes. Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness and abnormal cytokinesis were observed in low frequency. All abnormalities can compromise pollen viability by generating unbalanced gametes. Based on the chromosome number and meiotic stability, the present study indicates the apomictic tetraploid accessions that can act as male genitor to produce interspecific hybrids with B. ruziziensis or intraspecific hybrids with recently artificially tetraploidized accessions.

  6. Localization of latency-associated nuclear antigen (LANA) on mitotic chromosomes.

    Science.gov (United States)

    Rahayu, Retno; Ohsaki, Eriko; Omori, Hiroko; Ueda, Keiji

    2016-09-01

    In latent infection of Kaposi's sarcoma-associated herpesvirus (KSHV), viral gene expression is extremely limited and copy numbers of viral genomes remain constant. Latency-associated nuclear antigen (LANA) is known to have a role in maintaining viral genome copy numbers in growing cells. Several studies have shown that LANA is localized in particular regions on mitotic chromosomes, such as centromeres/pericentromeres. We independently examined the distinct localization of LANA on mitotic chromosomes during mitosis, using super-resolution laser confocal microscopy and correlative fluorescence microscopy-electron microscopy (FM-EM) analyses. We found that the majority of LANA were not localized at particular regions such as telomeres/peritelomeres, centromeres/pericentromeres, and cohesion sites, but at the bodies of condensed chromosomes. Thus, LANA may undergo various interactions with the host factors on the condensed chromosomes in order to tether the viral genome to mitotic chromosomes and realize faithful viral genome segregation during cell division. PMID:27254595

  7. PTEN regulates EG5 to control spindle architecture and chromosome congression during mitosis.

    Science.gov (United States)

    He, Jinxue; Zhang, Zhong; Ouyang, Meng; Yang, Fan; Hao, Hongbo; Lamb, Kristy L; Yang, Jingyi; Yin, Yuxin; Shen, Wen H

    2016-01-01

    Architectural integrity of the mitotic spindle is required for efficient chromosome congression and accurate chromosome segregation to ensure mitotic fidelity. Tumour suppressor PTEN has multiple functions in maintaining genome stability. Here we report an essential role of PTEN in mitosis through regulation of the mitotic kinesin motor EG5 for proper spindle architecture and chromosome congression. PTEN depletion results in chromosome misalignment in metaphase, often leading to catastrophic mitotic failure. In addition, metaphase cells lacking PTEN exhibit defects of spindle geometry, manifested prominently by shorter spindles. PTEN is associated and co-localized with EG5 during mitosis. PTEN deficiency induces aberrant EG5 phosphorylation and abrogates EG5 recruitment to the mitotic spindle apparatus, leading to spindle disorganization. These data demonstrate the functional interplay between PTEN and EG5 in controlling mitotic spindle structure and chromosome behaviour during mitosis. We propose that PTEN functions to equilibrate mitotic phosphorylation for proper spindle formation and faithful genomic transmission. PMID:27492783

  8. Reproductive outcome in 3 families with a satellited chromosome 4 with review of the literature

    Energy Technology Data Exchange (ETDEWEB)

    Arn, P.H.; Younie, L.; Russo, S. [Nemours Children`s Clinic, Jacksonville, FL (United States)] [and others

    1995-07-03

    We describe 3 families segregating for a translocation of the nucleolus organizer region (NOR) onto chromosome 4. Review of previously reported cases of translocations involving NOR and chromosome 4 shows that these translocations may be associated with variable reproductive outcomes. We provide evidence that imprinting is not the mechanism responsible for the variable reproductive outcomes in the case of satellited 4p chromosomes; this may offer indirect support for a ribosomal gene position effect. Translocated ribosomal genes may influence the expression of neighboring genes and could explain the variable phenotypes in individuals with satellited nonacrocentric chromosomes. We recommend that prenatal counseling of individuals with satellited nonacrocentric chromosomes should be cautious. 23 refs., 2 figs., 1 tab.

  9. CHROMOSOMES OF AMERICAN MARSUPIALS.

    Science.gov (United States)

    BIGGERS, J D; FRITZ, H I; HARE, W C; MCFEELY, R A

    1965-06-18

    Studies of the chromosomes of four American marsupials demonstrated that Caluromys derbianus and Marmosa mexicana have a diploid number of 14 chromosomes, and that Philander opossum and Didelphis marsupialis have a diploid number of 22. The karyotypes of C. derbianus and M. mexicana are similar, whereas those of P. opossum and D. marsupialis are dissimilar. If the 14-chromosome karyotype represents a reduction from a primitive number of 22, these observations suggest that the change has occurred independently in the American and Australasian forms.

  10. Segregation of unvoiced speech from nonspeech interference.

    Science.gov (United States)

    Hu, Guoning; Wang, DeLiang

    2008-08-01

    Monaural speech segregation has proven to be extremely challenging. While efforts in computational auditory scene analysis have led to considerable progress in voiced speech segregation, little attention has been given to unvoiced speech, which lacks harmonic structure and has weaker energy, hence more susceptible to interference. This study proposes a new approach to the problem of segregating unvoiced speech from nonspeech interference. The study first addresses the question of how much speech is unvoiced. The segregation process occurs in two stages: Segmentation and grouping. In segmentation, the proposed model decomposes an input mixture into contiguous time-frequency segments by a multiscale analysis of event onsets and offsets. Grouping of unvoiced segments is based on Bayesian classification of acoustic-phonetic features. The proposed model for unvoiced speech segregation joins an existing model for voiced speech segregation to produce an overall system that can deal with both voiced and unvoiced speech. Systematic evaluation shows that the proposed system extracts a majority of unvoiced speech without including much interference, and it performs substantially better than spectral subtraction. PMID:18681616

  11. 28 CFR 541.21 - Conditions of disciplinary segregation.

    Science.gov (United States)

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Conditions of disciplinary segregation... Conditions of disciplinary segregation. (a) Disciplinary segregation is the status of confinement of an... general population. Inmates housed in disciplinary segregation have significantly fewer privileges...

  12. What Should an Index of School Segregation Measure?

    Science.gov (United States)

    Allen, Rebecca; Vignoles, Anna

    2007-01-01

    The article aims to make a methodological contribution to the education segregation literature, providing a critique of previous measures of segregation used in the literature, as well as suggesting an alternative approach to measuring segregation. Specifically, the paper examines Gorard, Fitz and Taylor's finding that social segregation between…

  13. 41 CFR 109-1.5106 - Segregation of personal property.

    Science.gov (United States)

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Segregation of personal...-INTRODUCTION 1.51-Personal Property Management Standards and Practices § 109-1.5106 Segregation of personal...) The segregation of the property would materially hinder the progress of the work (i.e., segregation...

  14. Gender Segregation in the Spanish Labor Market: An Alternative Approach

    Science.gov (United States)

    del Rio, Coral; Alonso-Villar, Olga

    2010-01-01

    The aim of this paper is to study occupational segregation by gender in Spain, which is a country where occupational segregation explains a large part of the gender wage gap. As opposed to previous studies, this paper measures not only overall segregation, but also the segregation of several population subgroups. For this purpose, this paper uses…

  15. Interactive computer program for learning genetic principles of segregation and independent assortment through meiosis.

    Science.gov (United States)

    Yang, Xiaoli; Ge, Rong; Yang, Yufei; Shen, Hao; Li, Yingjie; Tseng, Charles C

    2009-01-01

    Teaching fundamental principles of genetics such as segregation and independent assortment of genes could be challenging for high school and college biology instructors. Students without thorough knowledge in meiosis often end up of frustration and failure in genetics courses. Although all textbooks and laboratory manuals have excellent graphic demonstrations and photographs of meiotic process, students may not always master the concept due to the lack of hands-on exercise. In response to the need for an effective lab exercise to understand the segregation of allelic genes and the independent assortment of the unlinked genes, we developed an interactive program for students to manually manipulate chromosome models and visualize each major step of meiosis so that these two genetic principles can be thoroughly understood.

  16. Matefin/SUN-1 phosphorylation is part of a surveillance mechanism to coordinate chromosome synapsis and recombination with meiotic progression and chromosome movement.

    Directory of Open Access Journals (Sweden)

    Alexander Woglar

    Full Text Available Faithful chromosome segregation during meiosis I depends on the establishment of a crossover between homologous chromosomes. This requires induction of DNA double-strand breaks (DSBs, alignment of homologs, homolog association by synapsis, and repair of DSBs via homologous recombination. The success of these events requires coordination between chromosomal events and meiotic progression. The conserved SUN/KASH nuclear envelope bridge establishes transient linkages between chromosome ends and cytoskeletal forces during meiosis. In Caenorhabditis elegans, this bridge is essential for bringing homologs together and preventing nonhomologous synapsis. Chromosome movement takes place during synapsis and recombination. Concomitant with the onset of chromosome movement, SUN-1 clusters at chromosome ends associated with the nuclear envelope, and it is phosphorylated in a chk-2- and plk-2-dependent manner. Identification of all SUN-1 phosphomodifications at its nuclear N terminus allowed us to address their role in prophase I. Failures in recombination and synapsis led to persistent phosphorylations, which are required to elicit a delay in progression. Unfinished meiotic tasks elicited sustained recruitment of PLK-2 to chromosome ends in a SUN-1 phosphorylation-dependent manner that is required for continued chromosome movement and characteristic of a zygotene arrest. Furthermore, SUN-1 phosphorylation supported efficient synapsis. We propose that signals emanating from a failure to successfully finish meiotic tasks are integrated at the nuclear periphery to regulate chromosome end-led movement and meiotic progression. The single unsynapsed X chromosome in male meiosis is precluded from inducing a progression delay, and we found it was devoid of a population of phosphorylated SUN-1. This suggests that SUN-1 phosphorylation is critical to delaying meiosis in response to perturbed synapsis. SUN-1 may be an integral part of a checkpoint system to monitor

  17. Single-nucleotide polymorphism versus microsatellite markers in a combined linkage and segregation analysis of a quantitative trait

    OpenAIRE

    Heath Simon C; Daw E Warwick; Lu Yue

    2005-01-01

    Abstract Increasingly, single-nucleotide polymorphism (SNP) markers are being used in preference to microsatellite markers. However, methods developed for microsatellites may be problematic when applied to SNP markers. We evaluated the results of using SNPs vs. microsatellites in Monte Carlo Markov chain (MCMC) oligogenic combined segregation and linkage analysis methods. These methods were developed with microsatellite markers in mind. We selected chromosome 7 from the Collaborative Study on...

  18. Mutations to the piRNA pathway component aubergine enhance meiotic drive of segregation distorter in Drosophila melanogaster.

    Science.gov (United States)

    Gell, Selena L; Reenan, Robert A

    2013-03-01

    Diploid sexual reproduction involves segregation of allelic pairs, ensuring equal representation of genotypes in the gamete pool. Some genes, however, are able to "cheat" the system by promoting their own transmission. The Segregation distorter (Sd) locus in Drosophila melanogaster males is one of the best-studied examples of this type of phenomenon. In this system the presence of Sd on one copy of chromosome 2 results in dysfunction of the non-Sd-bearing (Sd(+)) sperm and almost exclusive transmission of Sd to the next generation. The mechanism by which Sd wreaks such selective havoc has remained elusive. However, its effect requires a target locus on chromosome 2 known as Responder (Rsp). The Rsp locus comprises repeated copies of a satellite DNA sequence and Rsp copy number correlates with sensitivity to Sd. Under distorting conditions during spermatogenesis, nuclei with chromosomes containing greater than several hundred Rsp repeats fail to condense chromatin and are eliminated. Recently, Rsp sequences were found as small RNAs in association with Argonaute family proteins Aubergine (Aub) and Argonaute3 (AGO3). These proteins are involved in a germline-specific RNAi mechanism known as the Piwi-interacting RNA (piRNA) pathway, which specifically suppresses transposon activation in the germline. Here, we evaluate the role of piRNAs in segregation distortion by testing the effects of mutations to piRNA pathway components on distortion. Further, we specifically targeted mutations to the aub locus of a Segregation Distorter (SD) chromosome, using ends-out homologous recombination. The data herein demonstrate that mutations to piRNA pathway components act as enhancers of SD.

  19. Chromosomal abnormalities and autism

    Directory of Open Access Journals (Sweden)

    Farida El-Baz

    2016-01-01

    Conclusion: Chromosomal abnormalities were not detected in the studied autistic children, and so the relation between the genetics and autism still needs further work up with different study methods and techniques.

  20. Chromosome condensation and segmentation

    International Nuclear Information System (INIS)

    Some aspects of chromosome condensation in mammalians -humans especially- were studied by means of cytogenetic techniques of chromosome banding. Two further approaches were adopted: a study of normal condensation as early as prophase, and an analysis of chromosome segmentation induced by physical (temperature and γ-rays) or chemical agents (base analogues, antibiotics, ...) in order to show out the factors liable to affect condensation. Here 'segmentation' means an abnormal chromosome condensation appearing systematically and being reproducible. The study of normal condensation was made possible by the development of a technique based on cell synchronization by thymidine and giving prophasic and prometaphasic cells. Besides, the possibility of inducing R-banding segmentations on these cells by BrdU (5-bromodeoxyuridine) allowed a much finer analysis of karyotypes. Another technique was developed using 5-ACR (5-azacytidine), it allowed to induce a segmentation similar to the one obtained using BrdU and identify heterochromatic areas rich in G-C bases pairs

  1. Chromosomal Abnormalties with Epilepsy

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2005-02-01

    Full Text Available The correlation between specific chromosome abnormalties and various epilepsies was investigated by a study of 76 patients’ records obtained by questionnaires distributed to members of Kyoto Multi-institutional Study Group of Pediatric Neurology.

  2. Chimpanzee chromosome 13 is homologous to human chromosome 2p

    Energy Technology Data Exchange (ETDEWEB)

    Sun, N. C.; Sun, C. R.Y.; Ho, T.

    1977-01-01

    Similarities between human and chimpanzee chromosomes are shown by chromosome banding techniques and somatic cell hybridization techniques. Cell hybrids were obtained from the chimpanzee lymphocyte LE-7, and the Chinese hamster mutant cell, Gal-2. Experiments showed that the ACPL, MDHs, and Gal-Act genes could be assigned to chimpanzee chromosome 13, and since these genes have been assigned to human chromosme 2p, it is suggested that chimpanzee chromosome 13 is homologous to human chromosome 2p. (HLW)

  3. Chromosome doubling method

    Science.gov (United States)

    Kato, Akio

    2006-11-14

    The invention provides methods for chromosome doubling in plants. The technique overcomes the low yields of doubled progeny associated with the use of prior techniques for doubling chromosomes in plants such as grasses. The technique can be used in large scale applications and has been demonstrated to be highly effective in maize. Following treatment in accordance with the invention, plants remain amenable to self fertilization, thereby allowing the efficient isolation of doubled progeny plants.

  4. Segregation by thermal diffusion in granular shear flows

    OpenAIRE

    Garzó, Vicente; Reyes, Francisco Vega

    2010-01-01

    Segregation by thermal diffusion of an intruder immersed in a sheared granular gas is analyzed from the (inelastic) Boltzmann equation. Segregation is induced by the presence of a temperature gradient orthogonal to the shear flow plane and parallel to gravity. We show that, like in analogous systems without shear, the segregation criterion yields a transition between upwards segregation and downwards segregation. The form of the phase diagrams is illustrated in detail showing that they depend...

  5. Measuring Segregation: Basic Concepts and Extensions to Other Domains

    OpenAIRE

    Silber, Jacques

    2012-01-01

    This paper presents the main concepts used in measuring segregation. First it shows that the cardinal as well as the ordinal approach to the measurement of occupational segregation, when only two groups are considered (generally men and women), borrowed many ideas from the income inequality measurement literature. Second, it shows that more recent advances in segregation measurement, that were the consequence of an extension of segregation measures to the case of multi-group segregation and m...

  6. Industrial segregation of female and male workers in Spain

    OpenAIRE

    Olga Alonso-Villar; Coral del Río

    2009-01-01

    The aim of this paper is to study segregation in the Spanish labor market for both male and female workers, paying special attention to industrial segregation. As opposed to other studies, this article quantifies the segregation of each demographic group separately, rather than measuring overall segregation. For this purpose, it uses additively decomposable indices, together with local segregation curves, recently proposed in the literature, which allows us to go further in the empirical anal...

  7. A Measure of Segregation Based on Social Interactions

    OpenAIRE

    Echenique, Federico; Fryer, Roland

    2007-01-01

    We develop an index of segregation based on two premises: (1) a measure of segregation should disaggregate to the level of individuals, and (2) an individual is more segregated the more segregated are the agents with whom she interacts. We present an index that satisfies (1) and (2) and that is based on agents' social interactions: the extent to which blacks interact with blacks, whites with whites, etc. We use the index to measure school and residential segregation. Using detailed data on fr...

  8. A small (sSMC) chromosome 22 due to a maternal translocation between chromosomes 8 and 22: a case report.

    Science.gov (United States)

    Mundhofir, F E P; Kooper, A J A; Winarni, T I; Smits, A P T; Faradz, S M H; Hamel, B C J

    2010-01-01

    We report on a boy with partial trisomies for chromosomes 8 and 22 caused by the presence of a small supernumerary marker chromosome (sSMC), a der(22)t(8;22)(p22;q11.21), inherited from a t(8;22)(p22;q11.21) translocation carrier mother. He has mild mental retardation, unability to speak distinct words and several minor anomalies i.e. high forehead and hairline, telecanthus, upslanting palpebral fissures, depressed nasal bridge, nail hypoplasia, toe position anomaly and 5th finger clinodactyly. He has two maternal uncles and one maternal aunt with mental retardation. G-banding technique showed 47,XY,+mar whilst his mother's karyotype showed a balanced reciprocal translocation between the chromosomes 8 and 22. Fluorescence In Situ Hybridization (FISH) technique with probes for centromere 22 and 8pter were used to detect the origin of marker chromosome and confirmed the marker chromosome in the proband showing to be extra chromosomal material originated from chromosome 8 and 22. Additional genome wide microarray analysis, using the Affymetrix Nspl 250K SNP array platform was performed to further characterize the marker chromosome and resulted in a der(22)t(8;22)(p22;q11.21). Furthermore, cytogenetic analysis of three affected family members showed the same unbalanced translocation, due to 3:1 meiotic segregation. This indicated the viability of this unbalanced pattern and combined with the recurrent miscarriages by the proband's mother, the mechanism of transmitting extrachromosomal material is probably not a random process. Since, there is no similar translocation (8p;22q) reported and the chromosomal translocation largely exists of additional 8p22-8pter we compare the clinical outcomes with reported cases of 8p22-8pter triplication, although there is a part of genetic material derived from chromosome 22 present. This unique familial chromosome translocation case from Indonesia will give insight in the underlying mechanism of this recurrent chromosomal abnormality

  9. Physical Modeling of Dynamic Coupling between Chromosomal Loci.

    Science.gov (United States)

    Lampo, Thomas J; Kennard, Andrew S; Spakowitz, Andrew J

    2016-01-19

    The motion of chromosomal DNA is essential to many biological processes, including segregation, transcriptional regulation, recombination, and packaging. Physical understanding of these processes would be dramatically enhanced through predictive, quantitative modeling of chromosome dynamics of multiple loci. Using a polymer dynamics framework, we develop a prediction for the correlation in the velocities of two loci on a single chromosome or otherwise connected by chromatin. These predictions reveal that the signature of correlated motion between two loci can be identified by varying the lag time between locus position measurements. In general, this theory predicts that as the lag time interval increases, the dual-loci dynamic behavior transitions from being completely uncorrelated to behaving as an effective single locus. This transition corresponds to the timescale of the stress communication between loci through the intervening segment. This relatively simple framework makes quantitative predictions based on a single timescale fit parameter that can be directly compared to the in vivo motion of fluorescently labeled chromosome loci. Furthermore, this theoretical framework enables the detection of dynamically coupled chromosome regions from the signature of their correlated motion.

  10. Physical Modeling of Dynamic Coupling between Chromosomal Loci.

    Science.gov (United States)

    Lampo, Thomas J; Kennard, Andrew S; Spakowitz, Andrew J

    2016-01-19

    The motion of chromosomal DNA is essential to many biological processes, including segregation, transcriptional regulation, recombination, and packaging. Physical understanding of these processes would be dramatically enhanced through predictive, quantitative modeling of chromosome dynamics of multiple loci. Using a polymer dynamics framework, we develop a prediction for the correlation in the velocities of two loci on a single chromosome or otherwise connected by chromatin. These predictions reveal that the signature of correlated motion between two loci can be identified by varying the lag time between locus position measurements. In general, this theory predicts that as the lag time interval increases, the dual-loci dynamic behavior transitions from being completely uncorrelated to behaving as an effective single locus. This transition corresponds to the timescale of the stress communication between loci through the intervening segment. This relatively simple framework makes quantitative predictions based on a single timescale fit parameter that can be directly compared to the in vivo motion of fluorescently labeled chromosome loci. Furthermore, this theoretical framework enables the detection of dynamically coupled chromosome regions from the signature of their correlated motion. PMID:26789757

  11. pain2: A neuropathic pain QTL identified on rat chromosome 2.

    Science.gov (United States)

    Nissenbaum, Jonathan; Shpigler, Hagai; Pisanté, Anne; DelCanho, Sonia; Minert, Anne; Seltzer, Ze'ev; Devor, Marshall; Darvasi, Ariel

    2008-03-01

    We aimed to locate a chronic pain-associated QTL in the rat (Rattus norvegicus) based on previous findings of a QTL (pain1) on chromosome 15 of the mouse (Mus musculus). The work was based on rat selection lines HA (high autotomy) and LA (low autotomy) which show a contrasting pain phenotype in response to nerve injury in the neuroma model of neuropathic pain. An F(2) segregating population was generated from HA and LA animals. Phenotyped F(2) rats were genotyped on chromosome 7 and chromosome 2, regions that share a partial homology with mouse chromosome 15. Our interval mapping analysis revealed a LOD score value of 3.63 (corresponding to p=0.005 after correcting for multiple testing using permutations) on rat chromosome 2, which is suggestive of the presence of a QTL affecting the predisposition to neuropathic pain. This QTL was mapped to the 14-26cM interval of chromosome 2. Interestingly, this region is syntenic to mouse chromosome 13, rather than to the region of mouse chromosome 15 that contains pain1. This chromosomal position indicates that it is possibly a new QTL, and hence we name it pain2. Further work is needed to replicate and to uncover the underlying gene(s) in both species.

  12. Meiotic recombination, synapsis, meiotic inactivation and sperm aneuploidy in a chromosome 1 inversion carrier.

    Science.gov (United States)

    Kirkpatrick, Gordon; Chow, Victor; Ma, Sai

    2012-01-01

    Disrupted meiotic behaviour of inversion carriers may be responsible for suboptimal sperm parameters in these carriers. This study investigated meiotic recombination, synapsis, transcriptional silencing and chromosome segregation effects in a pericentric inv(1) carrier. Recombination (MLH1), synapsis (SYCP1, SYCP3) and transcriptional inactivation (γH2AX, BRCA1) were examined by fluorescence immunostaining. Chromosome specific rates of recombination were determined by fluorescence in-situ hybridization. Furthermore, testicular sperm was examined for aneuploidy and segregation of the inv(1). Our findings showed that global recombination rates were similar to controls. Recombination on the inv(1) and the sex chromosomes were reduced. The inv(1) associated with the XY body in 43.4% of cells, in which XY recombination was disproportionately absent, and 94.3% of cells displayed asynapsed regions which displayed meiotic silencing regardless of their association with the XY body. Furthermore, a low frequency of chromosomal imbalance was observed in spermatozoa (3.4%). Our results suggest that certain inversion carriers may display unimpaired global recombination and impaired recombination on the involved and the sex chromosomes during meiosis. Asynapsis or inversion-loop formation in the inverted region may be responsible for impaired spermatogenesis and may prevent sperm-chromosome imbalance.

  13. Cell division licensing in the multi-chromosomal Vibrio cholerae bacterium.

    Science.gov (United States)

    Galli, Elisa; Poidevin, Mickaël; Le Bars, Romain; Desfontaines, Jean-Michel; Muresan, Leila; Paly, Evelyne; Yamaichi, Yoshiharu; Barre, François-Xavier

    2016-01-01

    Cell division must be coordinated with chromosome replication and segregation to ensure the faithful transmission of genetic information during proliferation. In most bacteria, assembly of the division apparatus, the divisome, starts with the polymerization of a tubulin homologue, FtsZ, into a ring-like structure at mid-cell, the Z-ring(1). It typically occurs at half of the cell cycle when most of the replication and segregation cycle of the unique chromosome they generally harbour is achieved(2). The chromosome itself participates in the regulation of cell division, at least in part because it serves as a scaffold to position FtsZ polymerization antagonists(3). However, about 10% of bacteria have more than one chromosome(4), which raises questions about the way they license cell division(3). For instance, the genome of Vibrio cholerae, the agent of cholera, is divided between a 3 Mbp replicon that originates from the chromosome of its mono-chromosomal ancestor, Chr1, and a 1 Mbp plasmid-derived replicon, Chr2 (ref. 5). Here, we show that Chr2 harbours binding motifs for an inhibitor of Z-ring formation, which helps accurately position the V. cholerae divisome at mid-cell and postpones its assembly to the very end of the cell cycle. PMID:27562255

  14. Heterochromatic threads connect oscillating chromosomes during prometaphase I in Drosophila oocytes.

    Directory of Open Access Journals (Sweden)

    Stacie E Hughes

    2009-01-01

    Full Text Available In Drosophila oocytes achiasmate homologs are faithfully segregated to opposite poles at meiosis I via a process referred to as achiasmate homologous segregation. We observed that achiasmate homologs display dynamic movements on the meiotic spindle during mid-prometaphase. An analysis of living prometaphase oocytes revealed both the rejoining of achiasmate X chromosomes initially located on opposite half-spindles and the separation toward opposite poles of two X chromosomes that were initially located on the same half spindle. When the two achiasmate X chromosomes were positioned on opposite halves of the spindle their kinetochores appeared to display proper co-orientation. However, when both Xs were located on the same half spindle their kinetochores appeared to be oriented in the same direction. Thus, the prometaphase movement of achiasmate chromosomes is a congression-like process in which the two homologs undergo both separation and rejoining events that result in the either loss or establishment of proper kinetochore co-orientation. During this period of dynamic chromosome movement, the achiasmate homologs were connected by heterochromatic threads that can span large distances relative to the length of the developing spindle. Additionally, the passenger complex proteins Incenp and Aurora B appeared to localize to these heterochromatic threads. We propose that these threads assist in the rejoining of homologs and the congression of the migrating achiasmate homologs back to the main chromosomal mass prior to metaphase arrest.

  15. Kinetochore-independent chromosome poleward movement during anaphase of meiosis II in mouse eggs.

    Directory of Open Access Journals (Sweden)

    Manqi Deng

    Full Text Available Kinetochores are considered to be the key structures that physically connect spindle microtubules to the chromosomes and play an important role in chromosome segregation during mitosis. Due to different mechanisms of spindle assembly between centrosome-containing mitotic cells and acentrosomal meiotic oocytes, it is unclear how a meiotic spindle generates the poleward forces to drive two rounds of meiotic chromosome segregation to achieve genome haploidization. We took advantage of the fact that DNA beads are able to induce bipolar spindle formation without kinetochores and studied the behavior of DNA beads in the induced spindle in mouse eggs during meiosis II. Interestingly, DNA beads underwent poleward movements that were similar in timing and speed to the meiotic chromosomes, although all the beads moved together to the same spindle pole. Disruption of dynein function abolished the poleward movements of DNA beads but not of the meiotic chromosomes, suggesting the existence of different dynein-dependent and dynein-independent force generation mechanisms for the chromosome poleward movement, and the latter may be dependent on the presence of kinetochores. Consistent with the observed DNA bead poleward movement, sperm haploid chromatin (which also induced bipolar spindle formation after injection to a metaphase egg without forming detectable kinetochore structures also underwent similar poleward movement at anaphase as DNA beads. The results suggest that in the chromatin-induced meiotic spindles, kinetochore attachments to spindle microtubules are not absolutely required for chromatin poleward movements at anaphase.

  16. Racial Segregation and the American Foreclosure Crisis.

    Science.gov (United States)

    Rugh, Jacob S; Massey, Douglas S

    2010-10-01

    Although the rise in subprime lending and the ensuing wave of foreclosures was partly a result of market forces that have been well-identified in the literature, in the United States it was also a highly racialized process. We argue that residential segregation created a unique niche of poor minority clients who were differentially marketed risky subprime loans that were in great demand for use in mortgage-backed securities that could be sold on secondary markets. We test this argument by regressing foreclosure actions in the top 100 U.S. metropolitan areas on measures of black, Hispanic, and Asian segregation while controlling for a variety of housing market conditions, including average creditworthiness, the extent of coverage under the Community Reinvestment Act, the degree of zoning regulation, and the overall rate of subprime lending. We find that black residential dissimilarity and spatial isolation are powerful predictors of foreclosures across U.S. metropolitan areas. In order to isolate subprime lending as the causal mechanism whereby segregation influences foreclosures, we estimate a two-stage least squares model that confirms the causal effect of black segregation on the number and rate of foreclosures across metropolitan areas. In the United States segregation was an important contributing cause of the foreclosure crisis, along with overbuilding, risky lending practices, lax regulation, and the bursting of the housing price bubble. PMID:25308973

  17. Continuous utility factor in segregation models

    Science.gov (United States)

    Roy, Parna; Sen, Parongama

    2016-02-01

    We consider the constrained Schelling model of social segregation in which the utility factor of agents strictly increases and nonlocal jumps of the agents are allowed. In the present study, the utility factor u is defined in a way such that it can take continuous values and depends on the tolerance threshold as well as the fraction of unlike neighbors. Two models are proposed: in model A the jump probability is determined by the sign of u only, which makes it equivalent to the discrete model. In model B the actual values of u are considered. Model A and model B are shown to differ drastically as far as segregation behavior and phase transitions are concerned. In model A, although segregation can be achieved, the cluster sizes are rather small. Also, a frozen state is obtained in which steady states comprise many unsatisfied agents. In model B, segregated states with much larger cluster sizes are obtained. The correlation function is calculated to show quantitatively that larger clusters occur in model B. Moreover for model B, no frozen states exist even for very low dilution and small tolerance parameter. This is in contrast to the unconstrained discrete model considered earlier where agents can move even when utility remains the same. In addition, we also consider a few other dynamical aspects which have not been studied in segregation models earlier.

  18. Proteomics Analysis with a Nano Random Forest Approach Reveals Novel Functional Interactions Regulated by SMC Complexes on Mitotic Chromosomes.

    Science.gov (United States)

    Ohta, Shinya; Montaño-Gutierrez, Luis F; de Lima Alves, Flavia; Ogawa, Hiromi; Toramoto, Iyo; Sato, Nobuko; Morrison, Ciaran G; Takeda, Shunichi; Hudson, Damien F; Rappsilber, Juri; Earnshaw, William C

    2016-08-01

    Packaging of DNA into condensed chromosomes during mitosis is essential for the faithful segregation of the genome into daughter nuclei. Although the structure and composition of mitotic chromosomes have been studied for over 30 years, these aspects are yet to be fully elucidated. Here, we used stable isotope labeling with amino acids in cell culture to compare the proteomes of mitotic chromosomes isolated from cell lines harboring conditional knockouts of members of the condensin (SMC2, CAP-H, CAP-D3), cohesin (Scc1/Rad21), and SMC5/6 (SMC5) complexes. Our analysis revealed that these complexes associate with chromosomes independently of each other, with the SMC5/6 complex showing no significant dependence on any other chromosomal proteins during mitosis. To identify subtle relationships between chromosomal proteins, we employed a nano Random Forest (nanoRF) approach to detect protein complexes and the relationships between them. Our nanoRF results suggested that as few as 113 of 5058 detected chromosomal proteins are functionally linked to chromosome structure and segregation. Furthermore, nanoRF data revealed 23 proteins that were not previously suspected to have functional interactions with complexes playing important roles in mitosis. Subsequent small-interfering-RNA-based validation and localization tracking by green fluorescent protein-tagging highlighted novel candidates that might play significant roles in mitotic progression. PMID:27231315

  19. Segregation of Niobium During Electroslag Remelting Process

    Institute of Scientific and Technical Information of China (English)

    DONG Yan-wu; JIANG Zhou-hua; LI Zheng-bang

    2009-01-01

    Experiment was carried out after the process parameters were calculated by the model previously established.The relationship between interdendritic spacing and local solidification time (LST) mainly determined by process parameters was exposed.Furthermore,the extent of segregation was studied.The results indicate that LST and interdendritic spacing are the largest and the amount of Laves phase as a result of the niobium segregation is the highest in the center of the ingot,whereas the opposite results are obtained at the edge of ingot.The extent of element segregation and the amount of Laves phase can be reduced when appropriate parameters are used.Therefore,the duration of subsequent homogenization treatments for 718 is shortened and the alloy quality is improved.

  20. Genetic dosage and position effect of small supernumerary marker chromosome (sSMC) in human sperm nuclei in infertile male patient.

    Science.gov (United States)

    Olszewska, Marta; Wanowska, Elzbieta; Kishore, Archana; Huleyuk, Nataliya; Georgiadis, Andrew P; Yatsenko, Alexander N; Mikula, Mariya; Zastavna, Danuta; Wiland, Ewa; Kurpisz, Maciej

    2015-11-30

    Chromosomes occupy specific distinct areas in the nucleus of the sperm cell that may be altered in males with disrupted spermatogenesis. Here, we present alterations in the positioning of the human chromosomes 15, 18, X and Y between spermatozoa with the small supernumerary marker chromosome (sSMC; sSMC(+)) and spermatozoa with normal chromosome complement (sSMC(-)), for the first time described in the same ejaculate of an infertile, phenotypically normal male patient. Using classical and confocal fluorescent microscopy, the nuclear colocalization of chromosomes 15 and sSMC was analyzed. The molecular cytogenetic characteristics of sSMC delineated the karyotype as 47,XY,+der(15)(pter->p11.2::q11.1->q11.2::p11.2->pter)mat. Analysis of meiotic segregation showed a 1:1 ratio of sSMC(+) to sSMC(-) spermatozoa, while evaluation of sperm aneuploidy status indicated an increased level of chromosome 13, 18, 21 and 22 disomy, up to 7 × (2.7 - 15.1). Sperm chromatin integrity assessment did not reveal any increase in deprotamination in the patient's sperm chromatin. Importantly, we found significant repositioning of chromosomes X and Y towards the nuclear periphery, where both chromosomes were localized in close proximity to the sSMC. This suggests the possible influence of sSMC/XY colocalization on meiotic chromosome division, resulting in abnormal chromosome segregation, and leading to male infertility in the patient.

  1. Spatiotemporal choreography of chromosome and megaplasmids in the Sinorhizobium meliloti cell cycle.

    Science.gov (United States)

    Frage, Benjamin; Döhlemann, Johannes; Robledo, Marta; Lucena, Daniella; Sobetzko, Patrick; Graumann, Peter L; Becker, Anke

    2016-06-01

    A considerable share of bacterial species maintains multipartite genomes. Precise coordination of genome replication and segregation with cell growth and division is vital for proliferation of these bacteria. The α-proteobacterium Sinorhizobium meliloti possesses a tripartite genome composed of one chromosome and the megaplasmids pSymA and pSymB. Here, we investigated the spatiotemporal pattern of segregation of these S. meliloti replicons at single cell level. Duplication of chromosomal and megaplasmid origins of replication occurred spatially and temporally separated, and only once per cell cycle. Tracking of FROS (fluorescent repressor operator system)-labelled origins revealed a strict temporal order of segregation events commencing with the chromosome followed by pSymA and then by pSymB. The repA2B2C2 region derived from pSymA was sufficient to confer the spatiotemporal behaviour of this megaplasmid to a small plasmid. Altering activity of the ubiquitous prokaryotic replication initiator DnaA, either positively or negatively, resulted in an increase in replication initiation events or G1 arrest of the chromosome only. This suggests that interference with DnaA activity does not affect replication initiation control of the megaplasmids. PMID:26853523

  2. Etude du système de résolution des dimères de chromosome chez Vibrio cholerae - Implication dans le contrôle de la lysogénie du phage CTXφ codant pour la toxine cholérique

    OpenAIRE

    Val, Marie-Eve

    2008-01-01

    The majority of the bacteria have a single circular chromosome. At the time of replication, chromosome dimers can be formed by homologous recombination between sister chromatides. Dimerisation of replicating chromosomes prevents the faithful segregation of genetic information between the two daughter cells. To correct this, the tyrosine recombinases, XerC and XerD, resolve dimers by adding an additional crossover at a specific site on the chromosome called dif. In Escherichia coli, the resolu...

  3. Condensation and localization of the partitioning protein ParB on the bacterial chromosome

    OpenAIRE

    Broedersz, Chase P.; Wang, Xindan; Meir, Yigal; Loparo, Joseph J.; Rudner, David Z.; Wingreen, Ned S.

    2014-01-01

    The ParABS system is responsible for chromosome and plasmid segregation in many bacteria. A large, coherent ParB–DNA complex forms the partitioning module at the heart of this segregation machinery. Here we provide a simple theoretical model for interacting proteins on DNA to elucidate the structure of the ParB–DNA complex. We show that that both 3D bridging and 1D spreading interactions between DNA-bound ParB proteins are required to ensure the formation of a coherent protein–DNA complex. Th...

  4. Chemical segregation and self polarisation in ferroelectrics

    Directory of Open Access Journals (Sweden)

    Bernard E. Watts

    2009-06-01

    Full Text Available Chemical partitioning or segregation is commonly encountered in solid-state syntheses. It is driven by compositional, thermal and electric field gradients. These phenomena can be quite extreme in thin films and lead to notable effects on the electrical properties of ferroelectrics. The segregation in ferroelectric thin films will be illustrated and the mechanisms explained in terms of diffusion processes driven by a potential gradient of the oxygen. The hypothesis can also explain self polarisation and imprint in ferroelectric hysteresis.

  5. Carbon Segregation of Bearing Steel Concasting Billet

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The formation mechanism of “white band” and central carbon segregation of high-carbon Cr bearing steel concasting billets are discussed in this paper. The maximum oxygen content in the steel produced by concasting process was 13x10-6 with an average oxygen content of 9.3x 10-6.Comparison of metallurgical quality and fatigue property between the concasting steel (CC) andingot casting steel (IC) showed that the carbon segregation (C/C0) in former steel was 0.92~1.10and its fatigue life was equal to that of the latter steel.

  6. The role of chromosome missegregation in cancer development: a theoretical approach using agent-based modelling.

    Directory of Open Access Journals (Sweden)

    Arturo Araujo

    Full Text Available Many cancers are aneuploid. However, the precise role that chromosomal instability plays in the development of cancer and in the response of tumours to treatment is still hotly debated. Here, to explore this question from a theoretical standpoint we have developed an agent-based model of tissue homeostasis in which to test the likely effects of whole chromosome mis-segregation during cancer development. In stochastic simulations, chromosome mis-segregation events at cell division lead to the generation of a diverse population of aneuploid clones that over time exhibit hyperplastic growth. Significantly, the course of cancer evolution depends on genetic linkage, as the structure of chromosomes lost or gained through mis-segregation events and the level of genetic instability function in tandem to determine the trajectory of cancer evolution. As a result, simulated cancers differ in their level of genetic stability and in their growth rates. We used this system to investigate the consequences of these differences in tumour heterogeneity for anti-cancer therapies based on surgery and anti-mitotic drugs that selectively target proliferating cells. As expected, simulated treatments induce a transient delay in tumour growth, and reveal a significant difference in the efficacy of different therapy regimes in treating genetically stable and unstable tumours. These data support clinical observations in which a poor prognosis is correlated with a high level of chromosome mis-segregation. However, stochastic simulations run in parallel also exhibit a wide range of behaviours, and the response of individual simulations (equivalent to single tumours to anti-cancer therapy prove extremely variable. The model therefore highlights the difficulties of predicting the outcome of a given anti-cancer treatment, even in cases in which it is possible to determine the genotype of the entire set of cells within the developing tumour.

  7. Chromosome numbers in Bromeliaceae

    Directory of Open Access Journals (Sweden)

    Cotias-de-Oliveira Ana Lúcia Pires

    2000-01-01

    Full Text Available The present study reports chromosome numbers of 17 species of Bromeliaceae, belonging to the genera Encholirium, Bromelia, Orthophytum, Hohenbergia, Billbergia, Neoglaziovia, Aechmea, Cryptanthus and Ananas. Most species present 2n = 50, however, Bromelia laciniosa, Orthophytum burle-marxii and O. maracasense are polyploids with 2n = 150, 2n = 100 and 2n = 150, respectively, while for Cryptanthus bahianus, 2n = 34 + 1-4B. B chromosomes were observed in Bromelia plumieri and Hohenbergia aff. utriculosa. The chromosome number of all species was determined for the first time, except for Billbergia chlorosticta and Cryptanthus bahianus. Our data supports the hypothesis of a basic number of x = 25 for the Bromeliaceae family and decreasing aneuploidy in the genus Cryptanthus.

  8. Those amazing dinoflagellate chromosomes

    Institute of Scientific and Technical Information of China (English)

    PETER J RIZZO

    2003-01-01

    Dinoflagellates are a very large and diverse group of eukaryotic algae that play a major role in aquatic food webs of both fresh water and marine habitats. Moreover, the toxic members of this group pose a health threat in the form of red tides. Finally, dinoflagellates are of great evolutionary importance,because of their taxonomic position, and their unusual chromosome structure and composition. While the cytoplasm of dinoflagellates is typically eukaryotic, the nucleus is unique when compared to the nucleus of other eukaryotes. More specifically, while the chromosomes of all other eukaryotes contain histones,dinoflagellate chromosomes lack histones completely. There are no known exceptions to this observation: all dinoflagellates lack histones, and all other eukaryotes contain histones. Nevertheless, dinoflagellates remain a relatively unstudied group of eukaryotes.

  9. FtsK-dependent dimer resolution on multiple chromosomes in the pathogen Vibrio cholerae.

    Directory of Open Access Journals (Sweden)

    Marie-Eve Val

    Full Text Available Unlike most bacteria, Vibrio cholerae harbors two distinct, nonhomologous circular chromosomes (chromosome I and II. Many features of chromosome II are plasmid-like, which raised questions concerning its chromosomal nature. Plasmid replication and segregation are generally not coordinated with the bacterial cell cycle, further calling into question the mechanisms ensuring the synchronous management of chromosome I and II. Maintenance of circular replicons requires the resolution of dimers created by homologous recombination events. In Escherichia coli, chromosome dimers are resolved by the addition of a crossover at a specific site, dif, by two tyrosine recombinases, XerC and XerD. The process is coordinated with cell division through the activity of a DNA translocase, FtsK. Many E. coli plasmids also use XerCD for dimer resolution. However, the process is FtsK-independent. The two chromosomes of the V. cholerae N16961 strain carry divergent dimer resolution sites, dif1 and dif2. Here, we show that V. cholerae FtsK controls the addition of a crossover at dif1 and dif2 by a common pair of Xer recombinases. In addition, we show that specific DNA motifs dictate its orientation of translocation, the distribution of these motifs on chromosome I and chromosome II supporting the idea that FtsK translocation serves to bring together the resolution sites carried by a dimer at the time of cell division. Taken together, these results suggest that the same FtsK-dependent mechanism coordinates dimer resolution with cell division for each of the two V. cholerae chromosomes. Chromosome II dimer resolution thus stands as a bona fide chromosomal process.

  10. Somatic pairing, endomitosis and chromosome aberrations in snakes (Viperidae and Colubridae

    Directory of Open Access Journals (Sweden)

    Beçak Maria Luiza

    2003-01-01

    Full Text Available The positioning of macrochromosomes of Bothrops jararaca and Bothrops insularis (Viperidae was studied in undistorted radial metaphases of uncultured cells (spermatogonia and oogonia not subjected to spindle inhibitors. Colchicinized metaphases from uncultured (spleen and intestine and cultured tissues (blood were also analyzed. We report two antagonic non-random chromosome arrangements in untreated premeiotic cells: the parallel configuration with homologue chromosomes associated side by side in the metaphase plate and the antiparallel configuration having homologue chromosomes with antipolar distribution in the metaphase ring. The antiparallel aspect also appeared in colchicinized cells. The spatial chromosome arrangement in both configurations is groupal size-dependent and maintained through meiosis. We also describe, in untreated gonia cells, endomitosis followed by reductional mitosis which restores the diploid number. In B. jararaca males we observed that some gonad regions present changes in the meiotic mechanism. In this case, endoreduplicated cells segregate the diplochromosomes to opposite poles forming directly endoreduplicated second metaphases of meiosis with the suppression of first meiosis. By a successive division, these cells form nuclei with one set of chromosomes. Chromosome doubling in oogonia is known in hybrid species and in parthenogenetic salamanders and lizards. This species also presented chromosome rearrangements leading to aneuploidies in mitosis and meiosis. It is suggested that somatic pairing, endomitosis, meiotic alterations, and chromosomal aberrations can be correlated processes. Similar aspects of nuclei configurations, endomitosis and reductional mitosis were found in other Viperidae and Colubridae species.

  11. Loss of pRB causes centromere dysfunction and chromosomal instability.

    Science.gov (United States)

    Manning, Amity L; Longworth, Michelle S; Dyson, Nicholas J

    2010-07-01

    Chromosome instability (CIN) is a common feature of tumor cells. By monitoring chromosome segregation, we show that depletion of the retinoblastoma protein (pRB) causes rates of missegregation comparable with those seen in CIN tumor cells. The retinoblastoma tumor suppressor is frequently inactivated in human cancers and is best known for its regulation of the G1/S-phase transition. Recent studies have shown that pRB inactivation also slows mitotic progression and promotes aneuploidy, but reasons for these phenotypes are not well understood. Here we describe the underlying mitotic defects of pRB-deficient cells that cause chromosome missegregation. Analysis of mitotic cells reveals that pRB depletion compromises centromeric localization of CAP-D3/condensin II and chromosome cohesion, leading to an increase in intercentromeric distance and deformation of centromeric structure. These defects promote merotelic attachment, resulting in failure of chromosome congression and an increased propensity for lagging chromosomes following mitotic delay. While complete loss of centromere function or chromosome cohesion would have catastrophic consequences, these more moderate defects allow pRB-deficient cells to proliferate but undermine the fidelity of mitosis, leading to whole-chromosome gains and losses. These observations explain an important consequence of RB1 inactivation, and suggest that subtle defects in centromere function are a frequent source of merotely and CIN in cancer.

  12. Segregation--The Act of Sequestering

    Science.gov (United States)

    Foster, Charlotte

    2011-01-01

    In this article, the author points out that there are many reasons why self-segregation takes place. For example: People with motorcycle interests may choose to hang out with other bikers. A group of bikers may have a common interest but can be as diverse as a doctor that is a biker or a janitor that is into biking. Formally educated people may…

  13. 49 CFR 176.83 - Segregation.

    Science.gov (United States)

    2010-10-01

    ... Federal Register citations affecting § 176.83, see the List of CFR Sections Affected, which appears in the... 49 Transportation 2 2010-10-01 2010-10-01 false Segregation. 176.83 Section 176.83 Transportation..., DEPARTMENT OF TRANSPORTATION HAZARDOUS MATERIALS REGULATIONS CARRIAGE BY VESSEL General...

  14. Diversity, Racial Threat and Metropolitan Housing Segregation

    Science.gov (United States)

    DeFina, Robert; Hannon, Lance

    2009-01-01

    Previous studies have shown that as the percent black or percent Hispanic grows, that group's residential segregation from whites tends to increase as well. Typically, these findings are explained in terms of white discriminatory reaction to the perceived threat associated with minority population growth. The present analysis examines whether…

  15. Is Racial Segregation Changing in Charter Schools?

    Science.gov (United States)

    Lee, Jin; Lubienski, Christopher

    2011-01-01

    Charter schools embody the theoretical potential to promote integration since they can draw students from across district boundaries that often reflect segregated residential patterns. While a number of studies have examined overall racial composition of charter schools, virtually no attention has been paid to how charter school enrollment…

  16. Field induced phase segregation in ferrofluids

    NARCIS (Netherlands)

    Kooij, E.S.; Galca, A.C.; Poelsema, B.

    2008-01-01

    We study the phase segregation in magnetite ferrofluids under the influence of an external magnetic field. A phase with lower nanoparticle density and corresponding higher optical transmission is formed in the bottom of a glass cell in the presence of only a very modest magnetic field gradient (smal

  17. Msh2 deficiency leads to chromosomal abnormalities, centrosome amplification, and telomere capping defect

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yisong [ORNL; Liu, Yie [ORNL

    2006-01-01

    Msh2 is a key mammalian DNA mismatch repair (MMR) gene and mutations or deficiencies in mammalian Msh2 gene result in microsatellite instability (MSI+) and the development of cancer. Here, we report that primary mouse embryonic fibroblasts (MEFs) deficient in the murine MMR gene Msh2 (Msh2-/-) showed a significant increase in chromosome aneuploidy, centrosome amplification, and defective mitotic spindle organization and unequal chromosome segregation. Although Msh2-/- mouse tissues or primary MEFs had no apparent change in telomerase activity, telomere length, or recombination at telomeres, Msh2-/- MEFs showed an increase in chromosome end-to-end fusions or chromosome ends without detectable telomeric DNA. These data suggest that MSH2 helps to maintain genomic stability through the regulation of the centrosome and normal telomere capping in vivo and that defects in MMR can contribute to oncogenesis through multiple pathways.

  18. Sex segregation in undergraduate engineering majors

    Science.gov (United States)

    Litzler, Elizabeth

    Gender inequality in engineering persists in spite of women reaching parity in college enrollments and degrees granted. To date, no analyses of educational sex segregation have comprehensively examined segregation within one discipline. To move beyond traditional methods of studying the long-standing stratification by field of study in higher education, I explore gender stratification within one field: engineering. This dissertation investigates why some engineering disciplines have a greater representation of women than other engineering disciplines. I assess the individual and institutional factors and conditions associated with women's representation in certain engineering departments and compare the mechanisms affecting women's and men's choice of majors. I use national data from the Engineering Workforce Commission, survey data from 21 schools in the Project to Assess Climate in Engineering study, and Carnegie Foundation classification information to study sex segregation in engineering majors from multiple perspectives: the individual, major, institution, and country. I utilize correlations, t-tests, cross-tabulations, log-linear modeling, multilevel logistic regression and weighted least squares regression to test the relative utility of alternative explanations for women's disproportionate representation across engineering majors. As a whole, the analyses illustrate the importance of context and environment for women's representation in engineering majors. Hypotheses regarding hostile climate and discrimination find wide support across different analyses, suggesting that women's under-representation in certain engineering majors is not a question of choice or ability. However, individual level factors such as having engineering coursework prior to college show an especially strong association with student choice of major. Overall, the analyses indicate that institutions matter, albeit less for women, and women's under-representation in engineering is not

  19. The Y Chromosome

    Science.gov (United States)

    Offner, Susan

    2010-01-01

    The Y chromosome is of great interest to students and can be used to teach about many important biological concepts in addition to sex determination. This paper discusses mutation, recombination, mammalian sex determination, sex determination in general, and the evolution of sex determination in mammals. It includes a student activity that…

  20. Chromosomes, cancer and radiosensitivity

    International Nuclear Information System (INIS)

    Some specific chromosomal abnormalities are associated with certain cancers. The earliest description of such a specific association is the one of the Philadelphia chromosome and myelogenous leukemia (1960). Other congenital karyotype abnormalities are associated with specific cancers. Examples of these are Down's syndrome with leukemia and Klinefelter's syndrome with male breast cancer. Genetic diseases of increased chromosome breakage, or of defective chromosome repair, are associated with greatly increased cancer incidence. Three such diseases have been recognized: 1) Fanconi's anemia, associated with leukemias and lymphomas, 2) Bloom's syndrome, associated with acute leukemias and lymphosarcoma, and 3) ataxia telangiectasia, associated with Hodgkin's disease, leukemia, and lymphosarcomas. Ten percent of individuals with ataxia telangiectasia will develop one of these neoplasms. Individuals with certain of these syndromes display an unusually high radiosensitivity. Radiation therapy for cancers has been fatal in patients who received as low as 3000 rad. This remarkable radiosensitivity has been quantitated in cell cultures from such cases. Evidence suggests that the apparent sensitivity may reflect subnormal ability to repair radiation damage. The rapid proliferation of information in this field stems from the interdigitation of many disciplines and specialties, including cytogenetics, cell biology, molecular biology, epidemiology, radiobiology, and several others. This paper is intended for clinicians; it presents a structured analytic scheme for correlating and classifying this multidisciplinary information as it becomes available

  1. Chromosomes, cancer and radiosensitivity

    Energy Technology Data Exchange (ETDEWEB)

    Samouhos, E.

    1983-08-01

    Some specific chromosomal abnormalities are associated with certain cancers. The earliest description of such a specific association is the one of the Philadelphia chromosome and myelogenous leukemia (1960). Other congenital karyotype abnormalities are associated with specific cancers. Examples of these are Down's syndrome with leukemia and Klinefelter's syndrome with male breast cancer. Genetic diseases of increased chromosome breakage, or of defective chromosome repair, are associated with greatly increased cancer incidence. Three such diseases have been recognized: 1) Fanconi's anemia, associated with leukemias and lymphomas, 2) Bloom's syndrome, associated with acute leukemias and lymphosarcoma, and 3) ataxia telangiectasia, associated with Hodgkin's disease, leukemia, and lymphosarcomas. Ten percent of individuals with ataxia telangiectasia will develop one of these neoplasms. Individuals with certain of these syndromes display an unusually high radiosensitivity. Radiation therapy for cancers has been fatal in patients who received as low as 3000 rad. This remarkable radiosensitivity has been quantitated in cell cultures from such cases. Evidence suggests that the apparent sensitivity may reflect subnormal ability to repair radiation damage. The rapid proliferation of information in this field stems from the interdigitation of many disciplines and specialties, including cytogenetics, cell biology, molecular biology, epidemiology, radiobiology, and several others. This paper is intended for clinicians; it presents a structured analytic scheme for correlating and classifying this multidisciplinary information as it becomes available.

  2. Control on Housing Segregation:Housing Modes and Public Policies

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    <正>1. Housing segregation:advocating or controlling?The phenomenon of housing segregation has become more and more obvious in Chinese cities in recent years; however, there is no agreement on whether it should

  3. Measuring Trends in Segregation: Three Dimensions, Three Measures.

    Science.gov (United States)

    Stearns, Linda Brewster; Logan, John R.

    1986-01-01

    Three commonly used measures of segregation (index of dissimilarity, p* interaction probabilities, and the correlation ratio) reflect three conceptually distinct aspects of racial residential segregation. The results of empirical studies will depend on the measure chosen. (Author/KH)

  4. Telomere dysfunction and chromosome instability

    Energy Technology Data Exchange (ETDEWEB)

    Murnane, John P., E-mail: jmurnane@radonc.ucsf.edu [Department of Radiation Oncology, University of California San Francisco, 2340 Sutter Street, San Francisco, CA 94143-1331 (United States)

    2012-02-01

    The ends of chromosomes are composed of a short repeat sequence and associated proteins that together form a cap, called a telomere, that keeps the ends from appearing as double-strand breaks (DSBs) and prevents chromosome fusion. The loss of telomeric repeat sequences or deficiencies in telomeric proteins can result in chromosome fusion and lead to chromosome instability. The similarity between chromosome rearrangements resulting from telomere loss and those found in cancer cells implicates telomere loss as an important mechanism for the chromosome instability contributing to human cancer. Telomere loss in cancer cells can occur through gradual shortening due to insufficient telomerase, the protein that maintains telomeres. However, cancer cells often have a high rate of spontaneous telomere loss despite the expression of telomerase, which has been proposed to result from a combination of oncogene-mediated replication stress and a deficiency in DSB repair in telomeric regions. Chromosome fusion in mammalian cells primarily involves nonhomologous end joining (NHEJ), which is the major form of DSB repair. Chromosome fusion initiates chromosome instability involving breakage-fusion-bridge (B/F/B) cycles, in which dicentric chromosomes form bridges and break as the cell attempts to divide, repeating the process in subsequent cell cycles. Fusion between sister chromatids results in large inverted repeats on the end of the chromosome, which amplify further following additional B/F/B cycles. B/F/B cycles continue until the chromosome acquires a new telomere, most often by translocation of the end of another chromosome. The instability is not confined to a chromosome that loses its telomere, because the instability is transferred to the chromosome donating a translocation. Moreover, the amplified regions are unstable and form extrachromosomal DNA that can reintegrate at new locations. Knowledge concerning the factors promoting telomere loss and its consequences is

  5. ParABS system in chromosome partitioning in the bacterium Myxococcus xanthus.

    Directory of Open Access Journals (Sweden)

    Antonio A Iniesta

    Full Text Available Chromosome segregation is an essential cellular function in eukaryotic and prokaryotic cells. The ParABS system is a fundamental player for a mitosis-like process in chromosome partitioning in many bacterial species. This work shows that the social bacterium Myxococcus xanthus also uses the ParABS system for chromosome segregation. Its large prokaryotic genome of 9.1 Mb contains 22 parS sequences near the origin of replication, and it is shown here that M. xanthus ParB binds preferentially to a consensus parS sequence in vitro. ParB and ParA are essential for cell viability in M. xanthus as in Caulobacter crescentus, but unlike in many other bacteria. Absence of ParB results in anucleate cells, chromosome segregation defects and loss of viability. Analysis of ParA subcellular localization shows that it clusters at the poles in all cells, and in some, in the DNA-free cell division plane between two chromosomal DNA masses. This ParA localization pattern depends on ParB but not on FtsZ. ParB inhibits the nonspecific interaction of ParA with DNA, and ParA colocalizes with chromosomal DNA only when ParB is depleted. The subcellular localization of ParB suggests a single ParB-parS complex localized at the edge of the nucleoid, next to a polar ParA cluster, with a second ParB-parS complex migrating after the replication of parS takes place to the opposite nucleoid edge, next to the other polar ParA cluster.

  6. Effective Formation of the Segregation-Competent Complex Determines Successful Partitioning of the Bovine Papillomavirus Genome during Cell Division ▿ †

    OpenAIRE

    Silla, Toomas; Männik, Andres; Ustav, Mart

    2010-01-01

    Effective segregation of the bovine papillomavirus type 1 (BPV1), Epstein-Barr virus (EBV), and Kaposi's sarcoma-associated human herpesvirus type 8 (KSHV) genomes into daughter cells is mediated by a single viral protein that tethers viral genomes to host mitotic chromosomes. The linker proteins that mediate BPV1, EBV, and KSHV segregation are E2, LANA1, and EBNA1, respectively. The N-terminal transactivation domain of BPV1 E2 is responsible for chromatin attachment and subsequent viral geno...

  7. Workplace Segregation in the United States: Race, Ethnicity, and Skill

    OpenAIRE

    Judith Hellerstein; David Neumark

    2005-01-01

    We study workplace segregation in the United States using a unique matched employer-employee data set that we have created. We present measures of workplace segregation by education and language, and by race and ethnicity, and ­ since skill is often correlated with race and ethnicity ­ we assess the role of education- and language-related skill differentials in generating workplace segregation by race and ethnicity. We define segregation based on the extent to which workers are more or less l...

  8. What Drives Racial Segregation? New Evidence Using Census Microdata

    OpenAIRE

    Bayer, Patrick; McMillan, Robert; Rueben, Kim

    2003-01-01

    This paper sheds new light on the forces that drive residential segregation on the basis of race, assessing the extent to which across-race differences in other household characteristics can explain a significant portion of observed racial segregation. The central contribution of the analysis is to provide a transparent new measurement framework for understanding segregation patterns. This framework allows researchers to characterize patterns of segregation, to decompose them in meaningful wa...

  9. Segregation phases in a vibrated binary granular layer

    OpenAIRE

    Reis, P. M.; Ehrhardt, G.; Mullin, T.

    2003-01-01

    We present the results of an experimental study of patterned segregation in a horizontally shaken shallow layer of a binary mixture of dry particles. As the compacity, $C$, of the mixture was increased, the evolution of three distinct phases was observed. We classify them as binary gas, segregation liquid and segregation crystal phases using macroscopic and microscopic measures. The binary gas to segregation liquid transition is consistent with a continuous phase transition and includes the c...

  10. Occupational Gender Segregation in the Czech Republic (in English)

    OpenAIRE

    Štìpán Jurajda; Michal Franta

    2007-01-01

    The authors use labor force survey data to provide a detailed description and an international comparison of the level and structure of occupational gender segregation in the Czech Republic during 1994–2004. Based on 1999 data, they find Czech occupational segregation to be close to the EU average, with the exception of young, highly educated Czech workers, who faced relatively high segregation. However, segregation has declined rapidly for young workers since 1999, mainly due to the increase...

  11. Tipping and Residential Segregation: A Unified Schelling Model

    OpenAIRE

    Zhang, Junfu

    2009-01-01

    This paper presents a Schelling-type checkerboard model of residential segregation formulated as a spatial game. It shows that although every agent prefers to live in a mixed-race neighborhood, complete segregation is observed almost all of the time. A concept of tipping is rigorously defined, which is crucial for understanding the dynamics of segregation. Complete segregation emerges and persists in the checkerboard model precisely because tipping is less likely to occur to such residential ...

  12. Residential Segregation Effects on Poor’s Opportunities in Chile

    OpenAIRE

    Osvaldo Larrañaga Jiménez; Claudia Sanhueza Riveros

    2007-01-01

    This paper aims to identify whether or not the spatial concentration of poverty –also called economic residential segregation- affects the opportunities of the poor in Chile. Residential segregation is understood as the concentration particular population groups in determined geographical areas within cities. To identify the effects of segregation we use a panel of cross sections of the Casen household surveys, although the measures of segregation are computed from the Census data. The result...

  13. Effect of weightlessness on colloidal particle transport and segregation in self-organising microtubule preparations.

    Science.gov (United States)

    Tabony, James; Rigotti, Nathalie; Glade, Nicolas; Cortès, Sandra

    2007-05-01

    Weightlessness is known to effect cellular functions by as yet undetermined processes. Many experiments indicate a role of the cytoskeleton and microtubules. Under appropriate conditions in vitro microtubule preparations behave as a complex system that self-organises by a combination of reaction and diffusion. This process also results in the collective transport and organisation of any colloidal particles present. In large centimetre-sized samples, self-organisation does not occur when samples are exposed to a brief early period of weightlessness. Here, we report both space-flight and ground-based (clinorotation) experiments on the effect of weightlessness on the transport and segregation of colloidal particles and chromosomes. In centimetre-sized containers, both methods show that a brief initial period of weightlessness strongly inhibits particle transport. In miniature cell-sized containers under normal gravity conditions, the particle transport that self-organisation causes results in their accumulation into segregated regions of high and low particle density. The gravity dependence of this behaviour is strongly shape dependent. In square wells, neither self-organisation nor particle transport and segregation occur under conditions of weightlessness. On the contrary, in rectangular canals, both phenomena are largely unaffected by weightlessness. These observations suggest, depending on factors such as cell and embryo shape, that major biological functions associated with microtubule driven particle transport and organisation might be strongly perturbed by weightlessness.

  14. Screening of medicinal plants for induction of somatic segregation activity in Aspergillus nidulans.

    Science.gov (United States)

    Ramos Ruiz, A; De la Torre, R A; Alonso, N; Villaescusa, A; Betancourt, J; Vizoso, A

    1996-07-01

    Knowledge about mutagenic properties of plants commonly used in traditional medicine is limited. A screening for genotoxic activity was carried out in aqueous or alcoholic extracts prepared from 13 medicinal plants widely used as folk medicine in Cuba: Lepidium virginicum L. (Brassicaceae): Plantago major L. and Plantago lanceolata L. (Plantaginaceae); Ortosiphon aristatus Blume, Mentha x piperita L., Melissa officinalis L. and Plectranthus amboinicus (Lour.) Spreng. (Lamiaceae); Cymbopogon citratus (DC.) Stapf (Poaceae); Passiflora incarnata L. (Passifloraceae); Zingiber officinale Roscoe (Zingiberaceae); Piper auritum HBK. (Piperaceae); Schinus terebinthifolius Raddi (Anacardeaceae) and Momordica charantia L. (Cucurbitaceae). A plate incorporation assay with Aspergillus nidulans was employed, allowing detection of somatic segregation as a result of mitotic crossing-over, chromosome malsegregation or clastogenic effects. Aspergillus nidulans D-30, a well-marked strain carrying four recessive mutations for conidial color in heterozygosity, which permitted the direct visual detection of segregants, was used throughout this study. As a result, only in the aqueous extract of one of the plants screened (Momordica charantia) a statistical significant increase in the frequency of segregant sectors per colony was observed, and consequently, a genotoxic effect is postulated.

  15. Screening of medicinal plants for induction of somatic segregation activity in Aspergillus nidulans.

    Science.gov (United States)

    Ramos Ruiz, A; De la Torre, R A; Alonso, N; Villaescusa, A; Betancourt, J; Vizoso, A

    1996-07-01

    Knowledge about mutagenic properties of plants commonly used in traditional medicine is limited. A screening for genotoxic activity was carried out in aqueous or alcoholic extracts prepared from 13 medicinal plants widely used as folk medicine in Cuba: Lepidium virginicum L. (Brassicaceae): Plantago major L. and Plantago lanceolata L. (Plantaginaceae); Ortosiphon aristatus Blume, Mentha x piperita L., Melissa officinalis L. and Plectranthus amboinicus (Lour.) Spreng. (Lamiaceae); Cymbopogon citratus (DC.) Stapf (Poaceae); Passiflora incarnata L. (Passifloraceae); Zingiber officinale Roscoe (Zingiberaceae); Piper auritum HBK. (Piperaceae); Schinus terebinthifolius Raddi (Anacardeaceae) and Momordica charantia L. (Cucurbitaceae). A plate incorporation assay with Aspergillus nidulans was employed, allowing detection of somatic segregation as a result of mitotic crossing-over, chromosome malsegregation or clastogenic effects. Aspergillus nidulans D-30, a well-marked strain carrying four recessive mutations for conidial color in heterozygosity, which permitted the direct visual detection of segregants, was used throughout this study. As a result, only in the aqueous extract of one of the plants screened (Momordica charantia) a statistical significant increase in the frequency of segregant sectors per colony was observed, and consequently, a genotoxic effect is postulated. PMID:8771452

  16. Homoploid hybrid speciation and genome evolution via chromosome sorting

    Science.gov (United States)

    Lukhtanov, Vladimir A.; Shapoval, Nazar A.; Anokhin, Boris A.; Saifitdinova, Alsu F.; Kuznetsova, Valentina G.

    2015-01-01

    Genomes of numerous diploid plant and animal species possess traces of interspecific crosses, and many researches consider them as support for homoploid hybrid speciation (HHS), a process by which a new reproductively isolated species arises through hybridization and combination of parts of the parental genomes, but without an increase in ploidy. However, convincing evidence for a creative role of hybridization in the origin of reproductive isolation between hybrid and parental forms is extremely limited. Here, through studying Agrodiaetus butterflies, we provide proof of a previously unknown mode of HHS based on the formation of post-zygotic reproductive isolation via hybridization of chromosomally divergent parental species and subsequent fixation of a novel combination of chromosome fusions/fissions in hybrid descendants. We show that meiotic segregation, operating in the hybrid lineage, resulted in the formation of a new diploid genome, drastically rearranged in terms of chromosome number. We also demonstrate that during the heterozygous stage of the hybrid species formation, recombination was limited between rearranged chromosomes of different parental origin, representing evidence that the reproductive isolation was a direct consequence of hybridization. PMID:25925097

  17. Not Just Urban Policy: Suburbs, Segregation, and Charter Schools

    Science.gov (United States)

    Frankenberg, Erica; Siegel-Hawley, Genevieve

    2012-01-01

    As the charter school sector expands rapidly with federal support amid on-going diversification and growing segregation among traditional public school students, this article examines existing patterns of segregation in charter schools. Prior research has demonstrated that charter schools are substantially more segregated than our already…

  18. Segregation of Granular Mixtures in a Rotating Drum

    OpenAIRE

    Puri, Sanjay; Hayakawa, Hisao

    1999-01-01

    We formulate a phenomenological model for the segregation of binary mixtures of rough and smooth granular materials in a rotating drum. Our model successfully replicates a range of experimental behaviours, e.g., rapid radial segregation; slow axial segregation; and nonuniform radial structure of axial bands. We present some analytical results and detailed numerical results for our model.

  19. 49 CFR 176.145 - Segregation in single hold vessels.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Segregation in single hold vessels. 176.145 Section 176.145 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS... VESSEL Detailed Requirements for Class 1 (Explosive) Materials Segregation § 176.145 Segregation...

  20. What is the primary source of the morphological segregation?

    OpenAIRE

    Andreon, S.

    1997-01-01

    In Coma and two other clusters of galaxies the primary morphological segregation is the one with respect to a privileged direction. Only when this segregation is not considered it appears that the morphological types are segregated in density or in clustercentric distance.

  1. 27 CFR 24.27 - Segregation of operations.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Segregation of operations. 24.27 Section 24.27 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... Segregation of operations. The appropriate TTB officer may require the proprietor to segregate...

  2. Revisiting Residential Segregation by Income: A Monte Carlo Test

    OpenAIRE

    Junfu Zhang

    2003-01-01

    A long-standing hypothesis states that racial housing segregation in the U.S. results from the income inequalities between blacks and whites. This paper reexamines this hypothesis with a new methodology. We present a Monte Carlo study to show that segregation by income explains only a small proportion of the high level of segregation.

  3. Residential segregation of socioeconomic variables and health indices in Iran

    Directory of Open Access Journals (Sweden)

    Seyed Saeed Hashemi Nazari

    2013-01-01

    Conclusions: Correlation of segregation of determinants of socioeconomic status with segregation of health indices is an indicator of existence of hot zones of health problems across some provinces. Further studies using multilevel modeling and individual data in health outcomes at individual level and segregation measures at appropriate geographic levels are required to confirm these relations.

  4. "E Pluribus"... Separation: Deepening Double Segregation for More Students

    Science.gov (United States)

    Orfield, Gary; Kucsera, John; Siegel-Hawley, Genevieve

    2012-01-01

    This report shows segregation has increased dramatically across the country for Latino students, who are attending more intensely segregated and impoverished schools than they have for generations. The segregation increases have been the most dramatic in the West. The typical Latino student in the region attends a school where less than a quarter…

  5. 46 CFR 151.13-5 - Cargo segregation-tanks.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Cargo segregation-tanks. 151.13-5 Section 151.13-5... CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Cargo Segregation § 151.13-5 Cargo segregation—tanks. (a... symbols used in lines 1 and 2, in order, under the tank segregation column of Table 151.05....

  6. Chromosomal breakpoints characterization of two supernumerary ring chromosomes 20.

    Science.gov (United States)

    Guediche, N; Brisset, S; Benichou, J-J; Guérin, N; Mabboux, P; Maurin, M-L; Bas, C; Laroudie, M; Picone, O; Goldszmidt, D; Prévot, S; Labrune, P; Tachdjian, G

    2010-02-01

    The occurrence of an additional ring chromosome 20 is a rare chromosome abnormality, and no common phenotype has been yet described. We report on two new patients presenting with a supernumerary ring chromosome 20 both prenatally diagnosed. The first presented with intrauterine growth retardation and some craniofacial dysmorphism, and the second case had a normal phenotype except for obesity. Conventional cytogenetic studies showed for each patient a small supernumerary marker chromosome (SMC). Using fluorescence in situ hybridization, these SMCs corresponded to ring chromosomes 20 including a part of short and long arms of chromosome 20. Detailed molecular cytogenetic characterization showed different breakpoints (20p11.23 and 20q11.23 for Patient 1 and 20p11.21 and 20q11.21 for Patient 2) and sizes of the two ring chromosomes 20 (13.6 Mb for case 1 and 4.8 Mb for case 2). Review of the 13 case reports of an extra r(20) ascertained postnatally (8 cases) and prenatally (5 cases) showed varying degrees of phenotypic abnormalities. We document a detailed molecular cytogenetic chromosomal breakpoints characterization of two cases of supernumerary ring chromosomes 20. These results emphasize the need to characterize precisely chromosomal breakpoints of supernumerary ring chromosomes 20 in order to establish genotype-phenotype correlation. This report may be helpful for prediction of natural history and outcome, particularly in prenatal diagnosis.

  7. Linear Chromosome-generating System of Agrobacterium tumefaciens C58

    Science.gov (United States)

    Huang, Wai Mun; DaGloria, Jeanne; Fox, Heather; Ruan, Qiurong; Tillou, John; Shi, Ke; Aihara, Hideki; Aron, John; Casjens, Sherwood

    2012-01-01

    Agrobacterium tumefaciens C58, the pathogenic bacteria that causes crown gall disease in plants, harbors one circular and one linear chromosome and two circular plasmids. The telomeres of its unusual linear chromosome are covalently closed hairpins. The circular and linear chromosomes co-segregate and are stably maintained in the organism. We have determined the sequence of the two ends of the linear chromosome thus completing the previously published genome sequence of A. tumefaciens C58. We found that the telomeres carry nearly identical 25-bp sequences at the hairpin ends that are related by dyad symmetry. We further showed that its Atu2523 gene encodes a protelomerase (resolvase) and that the purified enzyme can generate the linear chromosomal closed hairpin ends in a sequence-specific manner. Agrobacterium protelomerase, whose presence is apparently limited to biovar 1 strains, acts via a cleavage-and-religation mechanism by making a pair of transient staggered nicks invariably at 6-bp spacing as the reaction intermediate. The enzyme can be significantly shortened at both the N and C termini and still maintain its enzymatic activity. Although the full-length enzyme can uniquely bind to its product telomeres, the N-terminal truncations cannot. The target site can also be shortened from the native 50-bp inverted repeat to 26 bp; thus, the Agrobacterium hairpin-generating system represents the most compact activity of all hairpin linear chromosome- and plasmid-generating systems to date. The biochemical analyses of the protelomerase reactions further revealed that the tip of the hairpin telomere may be unusually polymorphically capable of accommodating any nucleotide. PMID:22582388

  8. Familial complex chromosomal rearrangement resulting in a recombinant chromosome.

    Science.gov (United States)

    Berend, Sue Ann; Bodamer, Olaf A F; Shapira, Stuart K; Shaffer, Lisa G; Bacino, Carlos A

    2002-05-15

    Familial complex chromosomal rearrangements (CCRs) are rare and tend to involve fewer breakpoints and fewer chromosomes than CCRs that are de novo in origin. We report on a CCR identified in a child with congenital heart disease and dysmorphic features. Initially, the child's karyotype was thought to involve a straightforward three-way translocation between chromosomes 3, 8, and 16. However, after analyzing the mother's chromosomes, the mother was found to have a more complex rearrangement that resulted in a recombinant chromosome in the child. The mother's karyotype included an inverted chromosome 2 and multiple translocations involving chromosomes 3, 5, 8, and 16. No evidence of deletion or duplication that could account for the clinical findings in the child was identified.

  9. Ipl1/Aurora kinase suppresses S-CDK-driven spindle formation during prophase I to ensure chromosome integrity during meiosis.

    Directory of Open Access Journals (Sweden)

    Louise Newnham

    Full Text Available Cells coordinate spindle formation with DNA repair and morphological modifications to chromosomes prior to their segregation to prevent cell division with damaged chromosomes. Here we uncover a novel and unexpected role for Aurora kinase in preventing the formation of spindles by Clb5-CDK (S-CDK during meiotic prophase I and when the DDR is active in budding yeast. This is critical since S-CDK is essential for replication during premeiotic S-phase as well as double-strand break induction that facilitates meiotic recombination and, ultimately, chromosome segregation. Furthermore, we find that depletion of Cdc5 polo kinase activity delays spindle formation in DDR-arrested cells and that ectopic expression of Cdc5 in prophase I enhances spindle formation, when Ipl1 is depleted. Our findings establish a new paradigm for Aurora kinase function in both negative and positive regulation of spindle dynamics.

  10. [Chromosomal organization of the genomes of small-chromosome plants].

    Science.gov (United States)

    Muravenko, O V; Zelenin, A V

    2009-11-01

    An effective approach to study the chromosome organization in genomes of plants with small chromosomes and/or with low-informative C-banding patterns was developed in the course of investigation of the karyotypes of cotton plant, camomile, flax, and pea. To increase the resolving power of chromosome analysis, methods were worked out for revealing early replication patterns on chromosomes and for artificial impairment of mitotic chromosome condensation with the use of a DNA intercalator, 9-aminoacridine (9-AMA). To estimate polymorphism of the patterns of C-banding of small chromosomes on preparations obtained with the use of 9-AMA, it is necessary to choose a length interval that must not exceed three average sizes of metaphase chromosomes without the intercalator. The use of 9-AMA increases the resolution of differential C- and OR-banding and the precision of physical chromosome mapping by the FISH method. Of particular importance in studying small chromosomes is optimization of the computer-aided methods used to obtain and process chromosome images. The complex approach developed for analysis of the chromosome organization in plant genomes was used to study the karyotypes of 24 species of the genus Linum L. It permitted their chromosomes to be identified for the first time, and, in addition, B chromosomes were discovered and studied in the karyotypes of the species of the section Syllinum. By similarity of the karyotypes, the studied flax species were distributed in eight groups in agreement with the clusterization of these species according to the results of RAPD analysis performed in parallel. Systematic positions and phylogenetic relationships of the studied flax species were verified. Out results can serve as an important argument in favour of the proposal to develop a special program for sequencing the genome of cultivated flax (L. usitatissimum L.), which is a major representative of small-chromosome species. PMID:20058798

  11. Generative Models of Segregation: Investigating Model-Generated Patterns of Residential Segregation by Ethnicity and Socioeconomic Status

    OpenAIRE

    Fossett, Mark

    2011-01-01

    This paper considers the potential for using agent models to explore theories of residential segregation in urban areas. Results of generative experiments conducted using an agent-based simulation of segregation dynamics document that varying a small number of model parameters representing constructs from urban-ecological theories of segregation can generate a wide range of qualitatively distinct and substantively interesting segregation patterns. The results suggest how complex, macro-level ...

  12. From Schelling to Schools : A comparison of a model of residential segregation with a model of school segregation

    NARCIS (Netherlands)

    Stoica, Victor; Flache, Andreas

    2014-01-01

    We address theoretically whether and under what conditions Schelling's celebrated result of 'self-organized' unintended residential segregation may also apply to school segregation. We propose here a computational model of school segregation that is aligned with a corresponding Schelling-type model

  13. The requirement of p53 for maintaining chromosomal stability during tetraploidization

    OpenAIRE

    Ho, Chui Chui; Hau, Pok Man; Marxer, Miriam; Poon, Randy Y. C.

    2010-01-01

    Tetraploidization is believed to promote genome instability and tumorigenesis. Whether tetraploids per se are intrinsically unstable and transforming remain incompletely understood. In this report, tetraploidization was induced with cell fusion using mouse fibroblasts. Due to the unequal segregation of chromosomes during multipolar mitosis, the majority of cells were eliminated by p53-dependent mechanisms after tetraploidization. The rare tetraploid fibroblasts that were able to undergo bipol...

  14. A New Locus for Generalized Epilepsy with Febrile Seizures Plus Maps to Chromosome 2

    OpenAIRE

    Lopes-Cendes, I.; Scheffer, I E.; Berkovic, S F; Rousseau, M.; Andermann, E.; Rouleau, G. A.

    2000-01-01

    Generalized epilepsy with febrile seizures plus (GEFS+) is a recently recognized but relatively common form of inherited childhood-onset epilepsy with heterogeneous epilepsy phenotypes. We genotyped 41 family members, including 21 affected individuals, to localize the gene causing epilepsy in a large family segregating an autosomal dominant form of GEFS+. A genomewide search examining 197 markers identified linkage of GEFS+ to chromosome 2, on the basis of an initial positive LOD score for ma...

  15. Effects of container geometry on granular segregation pattern

    Institute of Scientific and Technical Information of China (English)

    Hu Mao-Bin; Kong Xiang-Zhao; Wu Qing-Song; Wu Yong-Hong

    2005-01-01

    In a set of vibrating quasi-two-dimensional containers with the right-hand sidewall bent inward, three new segregation patterns have been identified experimentally including a Two-Side segregation Pattern, a Left-hand Side segregation Pattern and a pattern where big particles aggregate to the upper left part of the container. In a container with small bending degree, either the two-side segregation pattern or the left-hand side segregation pattern is stable, which is determined by the initial distribution of particles.

  16. Construction of human chromosome 21-specific yeast artificial chromosomes.

    Science.gov (United States)

    McCormick, M K; Shero, J H; Cheung, M C; Kan, Y W; Hieter, P A; Antonarakis, S E

    1989-12-01

    Chromosome 21-specific yeast artificial chromosomes (YACs) have been constructed by a method that performs all steps in agarose, allowing size selection by pulsed-field gel electrophoresis and the use of nanogram to microgram quantities of DNA. The DNA sources used were hybrid cell line WAV-17, containing chromosome 21 as the only human chromosome and flow-sorted chromosome 21. The transformation efficiency of ligation products was similar to that obtained in aqueous transformations and yielded YACs with sizes ranging from 100 kilobases (kb) to greater than 1 megabase when polyamines were included in the transformation procedure. Twenty-five YACs containing human DNA have been obtained from a mouse-human hybrid, ranging in size from 200 to greater than 1000 kb, with an average size of 410 kb. Ten of these YACs were localized to subregions of chromosome 21 by hybridization of RNA probes (corresponding to the YAC ends recovered in Escherichia coli) to a panel of somatic cell hybrid DNA. Twenty-one human YACs, ranging in size from 100 to 500 kb, with an average size of 150 kb, were obtained from approximately equal to 50 ng of flow-sorted chromosome 21 DNA. Three were localized to subregions of chromosome 21. YACs will aid the construction of a physical map of human chromosome 21 and the study of disorders associated with chromosome 21 such as Alzheimer disease and Down syndrome.

  17. Phase diagram of a Schelling segregation model

    Science.gov (United States)

    Gauvin, L.; Vannimenus, J.; Nadal, J.-P.

    2009-07-01

    The collective behavior in a variant of Schelling’s segregation model is characterized with methods borrowed from statistical physics, in a context where their relevance was not conspicuous. A measure of segregation based on cluster geometry is defined and several quantities analogous to those used to describe physical lattice models at equilibrium are introduced. This physical approach allows to distinguish quantitatively several regimes and to characterize the transitions between them, leading to the building of a phase diagram. Some of the transitions evoke empirical sudden ethnic turnovers. We also establish links with ‘spin-1’ models in physics. Our approach provides generic tools to analyze the dynamics of other socio-economic systems.

  18. Segregation of polymers in confined spaces

    International Nuclear Information System (INIS)

    We investigate the motion of two overlapping polymers confined in a 2D box. A statistical model is constructed using blob-free-energy arguments. We find spontaneous segregation under the condition L > R∥, and mixing under L < R∥, where L is the length of the box and R∥ is the polymer extension in an infinite slit. The segregation time (τ) is determined by solving a mean first-passage time problem and by performing Monte Carlo simulations. Both show a minimum in τ as a function of L. Although our results are restricted to 2D, the basic mechanism of competition between entropy and confinement leading to the minimum is suggestive of an evolutionary driving force for size selection. (paper)

  19. Phase Segregation in Polystyrene?Polylactide Blends

    Energy Technology Data Exchange (ETDEWEB)

    Leung, Bonnie; Hitchcock, Adam; Brash, John; Scholl, Andreas; Doran, Andrew

    2010-06-09

    Spun-cast films of polystyrene (PS) blended with polylactide (PLA) were visualized and characterized using atomic force microscopy (AFM) and synchrotron-based X-ray photoemission electron microscopy (X-PEEM). The composition of the two polymers in these systems was determined by quantitative chemical analysis of near-edge X-ray absorption signals recorded with X-PEEM. The surface morphology depends on the ratio of the two components, the total polymer concentration, and the temperature of vacuum annealing. For most of the blends examined, PS is the continuous phase with PLA existing in discrete domains or segregated to the air?polymer interface. Phase segregation was improved with further annealing. A phase inversion occurred when films of a 40:60 PS:PLA blend (0.7 wt percent loading) were annealed above the glass transition temperature (Tg) of PLA.

  20. Coordination between chromosome replication, segregation, and cell division in Caulobacter crescentus

    DEFF Research Database (Denmark)

    Jensen, Rasmus Bugge

    2006-01-01

    Progression through the Caulobacter crescentus cell cycle is coupled to a cellular differentiation program. The swarmer cell is replicationally quiescent, and DNA replication initiates at the swarmer-to-stalked cell transition. There is a very short delay between initiation of DNA replication...

  1. INVESTIGATION OF POSSIBLE AGE EFFECTS ON MEIOTIC CHROMOSOMAL RECOMBINATION AND SEGREGATION IN ARMENIAN HAMSTER SPERMATOCYTES

    Science.gov (United States)

    Male Armenian hamsters (Cricetulus migratorius; 2N:22) were evaluated for age effects upon meiotic recombination and aneuploidy incidence. Primary spermatocytes from young and old animals revealed similar chiasma frequencies. The incidence of terminal-type chiasmata in sex bivale...

  2. Cdc37 is essential for chromosome segregation and cytokinesis in higher eukaryotes

    Science.gov (United States)

    Lange, Bodo M.H.; Rebollo, Elena; Herold, Andrea; González, Cayetano

    2002-01-01

    Cdc37 has been shown to be required for the activity and stability of protein kinases that regulate different stages of cell cycle progression. However, little is known so far regarding interactions of Cdc37 with kinases that play a role in cell division. Here we show that the loss of function of Cdc37 in Drosophila leads to defects in mitosis and male meiosis, and that these phenotypes closely resemble those brought about by the inactivation of Aurora B. We provide evidence that Aurora B interacts with and requires the Cdc37/Hsp90 complex for its stability. We conclude that the Cdc37/Hsp90 complex modulates the function of Aurora B and that most of the phenotypes brought about by the loss of Cdc37 function can be explained by the inactivation of this kinase. These observations substantiate the role of Cdc37 as an upstream regulatory element of key cell cycle kinases. PMID:12374737

  3. Human-Chromatin-Related Protein Interactions Identify a Demethylase Complex Required for Chromosome Segregation

    Directory of Open Access Journals (Sweden)

    Edyta Marcon

    2014-07-01

    Full Text Available Chromatin regulation is driven by multicomponent protein complexes, which form functional modules. Deciphering the components of these modules and their interactions is central to understanding the molecular pathways these proteins are regulating, their functions, and their relation to both normal development and disease. We describe the use of affinity purifications of tagged human proteins coupled with mass spectrometry to generate a protein-protein interaction map encompassing known and predicted chromatin-related proteins. On the basis of 1,394 successful purifications of 293 proteins, we report a high-confidence (85% precision network involving 11,464 protein-protein interactions among 1,738 different human proteins, grouped into 164 often overlapping protein complexes with a particular focus on the family of JmjC-containing lysine demethylases, their partners, and their roles in chromatin remodeling. We show that RCCD1 is a partner of histone H3K36 demethylase KDM8 and demonstrate that both are important for cell-cycle-regulated transcriptional repression in centromeric regions and accurate mitotic division.

  4. Functional Segregation of the Entopallium in Pigeons

    OpenAIRE

    Robert G Cook; Patton, Tadd B.; Shimizu, Toru

    2013-01-01

    In birds, the entopallium is the primary telencephalic target of the major visual ascending route called the tectofugal pathway. Often functionally compared to the primate geniculo-striate pathway and its subsequent telencephalic (cortical) regions, the latter processes visual information in a parallel fashion in terms of anatomy, physiology, and function. Little is known, however, about the exact mechanism of whether or how information is segregated or integrated in the avian tectofugal path...

  5. Segregation effects in DEEP2 galaxy groups

    Science.gov (United States)

    Nascimento, R. S.; Ribeiro, A. L. B.; Lopes, P. A. A.

    2016-09-01

    We investigate segregation phenomena in galaxy groups in the range of 0.2 low(z ≤ 0.6) and high (z > 0.6) redshift groups. Assuming that the color index (U - B)0 can be used as a proxy for the galaxy type, we found that the fraction of blue (star-forming) objects is higher in the high-z sample, with blue objects being dominant at MB > -19.5 for both samples, and red objects being dominant at MB low-z sample. Also, the radial variation of the red fraction indicates that there are more red objects with R low-z sample than in the high-z sample. Our analysis indicates statistical evidence of kinematic segregation, at the 99% c.l., for the low-z sample: redder and brighter galaxies present lower velocity dispersions than bluer and fainter ones. We also find a weaker evidence for spatial segregation between red and blue objects, at the 70% c.l. The analysis of the high-z sample reveals a different result: red and blue galaxies have velocity dispersion distributions not statistically distinct, although redder objects are more concentrated than the bluer ones at the 95% c.l. From the comparison of blue/red and bright/faint fractions, and considering the approximate lookback timescale between the two samples (˜3 Gyr), our results are consistent with a scenario where bright red galaxies had time to reach energy equipartition, while faint blue/red galaxies in the outskirts infall to the inner parts of the groups, thus reducing spatial segregation from z ˜ 0.8 to z ˜ 0.4.

  6. Biased DNA Segregation during Stem Cell Division

    OpenAIRE

    Anversa, Piero; Leri, Annarosa; Kajstura, Jan

    2012-01-01

    Adult skeletal muscle stem cells are a heterogeneous cell population characterized by a small subset of undifferentiated cells that express at high level the paired/homeodomain gene Pax7. This category of satellite cells divides predominantly by asymmetric chromatid segregation generating a daughter cell that carries the mother DNA and retains stem cell property, and a daughter cell that inherits the newly-synthesized DNA and acquires the myocyte lineage.1

  7. On impurity segregation on dislocations in metals

    OpenAIRE

    Netchaev, Yu.; Mukhina, L.

    1993-01-01

    Thermodynamic and crystallo-chemistry considerations are given about the possibility of existing linear distribution laws for some impurities in metals between bulk solution and near-dislocation segregation regions (NDSR) with composition and structure close to the corresponding intermetallic compound. The solutions of Fe in Al are considered. NDSR composition can be close to FeAl3. The experimental data on the solubilities are treated within the model developed to determine the effective bin...

  8. Sexual Segregation in Iberian Noctule Bats

    OpenAIRE

    Ibáñez, Carlos; Guillén, Antonio; Agirre-Mendi, Pablo T.; Juste, Javier; Schreur, Godfried; Cordero, Ana I.; Popa-Lisseanu, Ana G.

    2009-01-01

    Sexual segregation during the breeding season is common in many temperate bat species, and may be related to sex-specific thermoregulatory, microclimatic, or energetic requirements. We compiled capture data for 3 species of Nyctalus (noctule bats) obtained over .20 years to study reproductive and migratory strategies of these species in southwestern Europe. Within the Iberian Peninsula, several different strategies regarding sex distribution and migratory behavior were observed within each o...

  9. A Spatially Extended Model for Residential Segregation

    OpenAIRE

    Antonio Aguilera; Edgardo Ugalde

    2006-01-01

    We analyze urban spatial segregation phenomenon in terms of the income distribution over a population, and an inflationary parameter weighting the evolution of housing prices. For this, we develop a discrete spatially extended model based on a multiagent approach. In our model, the mobility of socioeconomic agents is driven only by the housing prices. Agents exchange location in order to fit their status to the cost of their ...

  10. SOLID WASTE SEGREGATION BEHAVIOR AMONG URBAN WOMEN

    OpenAIRE

    P. Mohamed Nisha; Raji Sugumar

    2014-01-01

    This study examined the solid waste segregation behavior of the women of Chennai city of Tamil Nadu state. Using a structured, self-developed interview schedule, 120 women were selected randomly for the survey with equal representation from the three regions of Chennai city. Findings revealed that most of the waste that is being generated in the households of the selected samples was organic, recyclable and reusable. The sample women are not highly knowledgeable about the solid...

  11. Segregation patterns in gas-fluidized systems

    OpenAIRE

    Gilbertson, M.A.; Eames, I

    2001-01-01

    The formation of segregation patterns in initially homogeneous, fluidized, binary mixtures of particles has been studied. The adjustment of the bed depends on the proportions of fine and coarse particles in the mixture and the gas flow rate relative to the minimum fluidization velocities of the two components. The particles are immobile until the gas flow rate is sufficiently large to fluidize the mixture of particles. When the gas how rate exceeds this critical value, alternating vertical ba...

  12. Evaluating segregation in granular filters for earth dams

    Energy Technology Data Exchange (ETDEWEB)

    Sutherland, K. [Cambridge Univ., Cambridge (United Kingdom); Grabinsky, M. [Toronto Univ., ON (Canada)

    2003-07-01

    This paper presented some case studies to illustrate the relationship between seepage problems encountered with earth dams and segregation of the dams' granular filters during construction. A literature review of segregation mechanisms was presented along with a laboratory investigation. The case studies showed that the current understanding of the impact of a given degree of segregation is relatively poor. The literature reveals that although segregation mechanisms are identified and analyzed, very few are likely to be predominant during earth dam construction. Laboratory studies show that a mathematical relationship can be established between the filter's grain size distribution curve and the potential degree of segregation. Therefore, a mathematical relationship can also be established with the potential for adverse dam performance. The authors proposed a field procedure which allows for the monitoring of segregation during construction by contractors and engineers. It also helps in deciding whether any segregated zones require replacement. 5 refs., 7 figs.

  13. Segregation by thermal diffusion in granular shear flows

    International Nuclear Information System (INIS)

    Segregation by thermal diffusion of an intruder immersed in a sheared granular gas is analyzed from the (inelastic) Boltzmann equation. Segregation is induced by the presence of a temperature gradient orthogonal to the shear flow plane and parallel to gravity. We show that, like in analogous systems without shear, the segregation criterion yields a transition between upwards segregation and downwards segregation. The form of the phase diagrams is illustrated in detail showing that they depend sensitively on the value of gravity relative to the thermal gradient. Two specific situations are considered: (i) absence of gravity and (ii) homogeneous temperature. We find that both mechanisms (upwards and downwards segregation) are stronger and more clearly separated when compared with segregation criteria in systems without shear

  14. Distribution and segregation of dissolved elements in pipeline slab

    Institute of Scientific and Technical Information of China (English)

    Jianhua Liu; Yanping Bao; Xian Dong; Taiquan Li; Yi Ren; Shuai Zhang

    2007-01-01

    The chemical composition in a cross section of a high grade pipeline slab was measured point by point (in a scale of 1 μm)using original position statistic distribution analysis (OPA). The result indicated that negative segregation strips of Si, Mn, Mo, Ni, Cr,Nb, Cu, Ti, and V exist in the two sides 24 mm away from the central line, with a width of 8-12 mm, Negative segregation inside the central line is more severe than that outside the central line, and the highest positive segregation of the elements appears closely by the inner sides of the negative segregation strips. No obvious negative segregation strip of S and P is found. Segregation of the elements in the central area is higher than that in the outer and inner arc areas. The segregation of C, Ti, S, and P is high and that of Cr, Cu, Si, and Mn is low in the slab.

  15. Implementing spatial segregation measures in R.

    Directory of Open Access Journals (Sweden)

    Seong-Yun Hong

    Full Text Available Reliable and accurate estimation of residential segregation between population groups is important for understanding the extent of social cohesion and integration in our society. Although there have been considerable methodological advances in the measurement of segregation over the last several decades, the recently developed measures have not been widely used in the literature, in part due to their complex calculation. To address this problem, we have implemented several newly proposed segregation indices in R, an open source software environment for statistical computing and graphics, as a package called seg. Although there are already a few standalone applications and add-on packages that provide access to similar methods, our implementation has a number of advantages over the existing tools. First, our implementation is flexible in the sense that it provides detailed control over the calculation process with a wide range of input parameters. Most of the parameters have carefully chosen defaults, which perform acceptably in many situations, so less experienced users can also use the implemented functions without too much difficulty. Second, there is no need to export results to other software programs for further analysis. We provide coercion methods that enable the transformation of our output classes into general R classes, so the user can use thousands of standard and modern statistical techniques, which are already available in R, for the post-processing of the results. Third, our implementation does not require commercial software to operate, so it is accessible to a wider group of people.

  16. Segregation effects in DEEP2 galaxy groups

    CERN Document Server

    Nascimento, Raquel S; Lopes, Paulo A A

    2016-01-01

    We investigate segregation phenomena in galaxy groups in the range of $0.20.6$) redshift groups. Assuming that the color index ${(U-B)_0}$ can be used as a proxy for the galaxy type, we found that the fraction of blue (star-forming) objects is higher in the high-z sample, with blue objects being dominant at $M_{B}>-19.5$ for both samples, and red objects being dominant at $M_{B}<-19.5$ only for the low-z sample. Also, the radial variation of the red fraction indicates that there are more red objects with $Rsegregation, at the 99%c.l., for the low-z sample: redder and brighter galaxies present lower velocity dispersions than bluer and fainter ones. We also find a weaker evidence for spatial segregation between red and blue objects, at the 70%c.l. The analysis of the high-z sample reveals a different result: red and blue galaxies have velocity dispersion distributions not statistically distinc...

  17. How population structure shapes neighborhood segregation.

    Science.gov (United States)

    Bruch, Elizabeth E

    2014-03-01

    This study provides a framework for understanding how population composition conditions the relationship between individuals' choices about group affiliation and aggregate patterns of social separation or integration. The substantive focus is the role of income inequality in racial residential segregation. The author identifies three population parameters--between-group inequality, within-group inequality, and relative group size--that determine how income inequality between race groups affects racial segregation. She uses data from the Panel Study of Income Dynamics to estimate models of individual-level residential mobility and incorporates these estimates into agent-based models. She then simulates segregation dynamics under alternative assumptions about (1) the relative size of minority groups and (2) the degree of correlation between race and income among individuals. The author finds that income inequality can have offsetting effects at the high and low ends of the income distribution. She demonstrates the empirical relevance of the simulation results using fixed-effects, metro-level regressions applied to 1980-2000 U.S. census data. PMID:25009360

  18. Implementing spatial segregation measures in R.

    Science.gov (United States)

    Hong, Seong-Yun; O'Sullivan, David; Sadahiro, Yukio

    2014-01-01

    Reliable and accurate estimation of residential segregation between population groups is important for understanding the extent of social cohesion and integration in our society. Although there have been considerable methodological advances in the measurement of segregation over the last several decades, the recently developed measures have not been widely used in the literature, in part due to their complex calculation. To address this problem, we have implemented several newly proposed segregation indices in R, an open source software environment for statistical computing and graphics, as a package called seg. Although there are already a few standalone applications and add-on packages that provide access to similar methods, our implementation has a number of advantages over the existing tools. First, our implementation is flexible in the sense that it provides detailed control over the calculation process with a wide range of input parameters. Most of the parameters have carefully chosen defaults, which perform acceptably in many situations, so less experienced users can also use the implemented functions without too much difficulty. Second, there is no need to export results to other software programs for further analysis. We provide coercion methods that enable the transformation of our output classes into general R classes, so the user can use thousands of standard and modern statistical techniques, which are already available in R, for the post-processing of the results. Third, our implementation does not require commercial software to operate, so it is accessible to a wider group of people. PMID:25415326

  19. A Spatially Extended Model for Residential Segregation

    Directory of Open Access Journals (Sweden)

    Antonio Aguilera

    2007-01-01

    Full Text Available We analyze urban spatial segregation phenomenon in terms of the income distribution over a population, and an inflationary parameter weighting the evolution of housing prices. For this, we develop a discrete spatially extended model based on a multiagent approach. In our model, the mobility of socioeconomic agents is driven only by the housing prices. Agents exchange location in order to fit their status to the cost of their housing. On the other hand, the price of a particular house depends on the status of its tenant, and on the neighborhood mean lodging cost weighted by a control parameter. The agent's dynamics converges to a spatially organized configuration, whose regularity is measured by using an entropy-like indicator. This simple model provides a dynamical process organizing the virtual city, in a way that the population inequality and the inflationary parameter determine the degree of residential segregation in the final stage of the process, in agreement with the segregation-inequality thesis put forward by Douglas Massey.

  20. Minimization and segregation of radioactive wastes

    International Nuclear Information System (INIS)

    The report will serve as one of a series of technical manuals providing reference material and direct know-how to staff in radioisotope user establishments and research centres in Member States without nuclear power and the associated range of complex waste management operations. Considerations are limited to the minimization and segregation of wastes, these being initial steps on which the efficiency of the whole waste management system depends. The minimization and segregation operations are examined in the context of the restricted quantities and predominantly shorter lived activities of wastes from nuclear research, production and usage of radioisotopes. Liquid and solid wastes only are considered in the report. Gaseous waste minimization and treatment are specialized subjects and are not examined in this document. Gaseous effluent treatment in facilities handling low and intermediate level radioactive materials has been already the subject of a detailed IAEA report. Management of spent sealed sources has specifically been covered in a previous manual. Conditioned sealed sources must be taken into account in segregation arrangements for interim storage and disposal where there are exceptional long lived highly radiotoxic isotopes, particularly radium or americium. These are unlikely ever to be suitable for shallow land burial along with the remaining wastes. 30 refs, 5 figs, 8 tabs

  1. Integration and segregation in auditory scene analysis

    Science.gov (United States)

    Sussman, Elyse S.

    2005-03-01

    Assessment of the neural correlates of auditory scene analysis, using an index of sound change detection that does not require the listener to attend to the sounds [a component of event-related brain potentials called the mismatch negativity (MMN)], has previously demonstrated that segregation processes can occur without attention focused on the sounds and that within-stream contextual factors influence how sound elements are integrated and represented in auditory memory. The current study investigated the relationship between the segregation and integration processes when they were called upon to function together. The pattern of MMN results showed that the integration of sound elements within a sound stream occurred after the segregation of sounds into independent streams and, further, that the individual streams were subject to contextual effects. These results are consistent with a view of auditory processing that suggests that the auditory scene is rapidly organized into distinct streams and the integration of sequential elements to perceptual units takes place on the already formed streams. This would allow for the flexibility required to identify changing within-stream sound patterns, needed to appreciate music or comprehend speech..

  2. Autosomal dominant congenital cataract in a Libyan Jewish family: cosegregation with a reciprocal chromosomal translocation [t(3;5)(p22.3; p15.1)

    OpenAIRE

    Zafer, Emre; Meck, Jeanne; Gerrad, Liora; Pras, Elon; Frydman, Moshe; Reish, Orit; Avni, Isaac; Pras, Eran

    2008-01-01

    Purpose To describe a Jewish family of Libyan ancestry in which autosomal dominant congenital cataract segregates with an apparently balanced reciprocal chromosomal translocation. Methods Detailed family history and clinical data were recorded. Cytogenetic studies were performed on 13 family members. Results Embryonal cataracts cosegregated through three generations with a balanced chromosomal translocation [t(3;5)(p22.3; p15.1)] while the unbalanced translocation product, 46,XY,-5,+der(5)t(3...

  3. Meiotic chromosome mobility in fission yeast is resistant to environmental stress.

    Science.gov (United States)

    Illner, Doris; Lorenz, Alexander; Scherthan, Harry

    2016-01-01

    The formation of healthy gametes requires pairing of homologous chromosomes (homologs) as a prerequisite for their correct segregation during meiosis. Initially, homolog alignment is promoted by meiotic chromosome movements feeding into intimate homolog pairing by homologous recombination and/or synaptonemal complex formation. Meiotic chromosome movements in the fission yeast, Schizosaccharomyces pombe, depend on astral microtubule dynamics that drag the nucleus through the zygote; known as horsetail movement. The response of microtubule-led meiotic chromosome movements to environmental stresses such as ionizing irradiation (IR) and associated reactive oxygen species (ROS) is not known. Here, we show that, in contrast to budding yeast, the horsetail movement is largely radiation-resistant, which is likely mediated by a potent antioxidant defense. IR exposure of sporulating S. pombe cells induced misrepair and irreparable DNA double strand breaks causing chromosome fragmentation, missegregation and gamete death. Comparing radiation outcome in fission and budding yeast, and studying meiosis with poisoned microtubules indicates that the increased gamete death after IR is innate to fission yeast. Inhibition of meiotic chromosome mobility in the face of IR failed to influence the course of DSB repair, indicating that paralysis of meiotic chromosome mobility in a genotoxic environment is not a universal response among species. PMID:27074839

  4. Destabilized SMC5/6 complex leads to chromosome breakage syndrome with severe lung disease.

    Science.gov (United States)

    van der Crabben, Saskia N; Hennus, Marije P; McGregor, Grant A; Ritter, Deborah I; Nagamani, Sandesh C S; Wells, Owen S; Harakalova, Magdalena; Chinn, Ivan K; Alt, Aaron; Vondrova, Lucie; Hochstenbach, Ron; van Montfrans, Joris M; Terheggen-Lagro, Suzanne W; van Lieshout, Stef; van Roosmalen, Markus J; Renkens, Ivo; Duran, Karen; Nijman, Isaac J; Kloosterman, Wigard P; Hennekam, Eric; Orange, Jordan S; van Hasselt, Peter M; Wheeler, David A; Palecek, Jan J; Lehmann, Alan R; Oliver, Antony W; Pearl, Laurence H; Plon, Sharon E; Murray, Johanne M; van Haaften, Gijs

    2016-08-01

    The structural maintenance of chromosomes (SMC) family of proteins supports mitotic proliferation, meiosis, and DNA repair to control genomic stability. Impairments in chromosome maintenance are linked to rare chromosome breakage disorders. Here, we have identified a chromosome breakage syndrome associated with severe lung disease in early childhood. Four children from two unrelated kindreds died of severe pulmonary disease during infancy following viral pneumonia with evidence of combined T and B cell immunodeficiency. Whole exome sequencing revealed biallelic missense mutations in the NSMCE3 (also known as NDNL2) gene, which encodes a subunit of the SMC5/6 complex that is essential for DNA damage response and chromosome segregation. The NSMCE3 mutations disrupted interactions within the SMC5/6 complex, leading to destabilization of the complex. Patient cells showed chromosome rearrangements, micronuclei, sensitivity to replication stress and DNA damage, and defective homologous recombination. This work associates missense mutations in NSMCE3 with an autosomal recessive chromosome breakage syndrome that leads to defective T and B cell function and acute respiratory distress syndrome in early childhood. PMID:27427983

  5. From Schelling to Schools: A Comparison of a Model of Residential Segregation with a Model of School Segregation

    OpenAIRE

    Victor Ionut Stoica; Andreas Flache

    2014-01-01

    We address theoretically whether and under what conditions Schelling’s celebrated result of ‘self-organized’ unintended residential segregation may also apply to school segregation. We propose here a computational model of school segregation that is aligned with a corresponding Schelling-type model of residential segregation. To adapt the model for application to school segregation, we move beyond previous work by combining two preference arguments in modeling parents’ school choice, ...

  6. Microsatellite marker analysis of an anther-derived potato family: skewed segregation and gene-centromere mapping.

    Science.gov (United States)

    Chani, Eduard; Ashkenazi, Varda; Hillel, Jossi; Veilleux, Richard E

    2002-04-01

    Segregation patterns of polymorphic simple sequence repeat (SSR) primer pairs were investigated in monoploid potato families derived from anther culture. A total of 14 primers developed from the sequences in the database, as well as from a genomic library of potato, was used. Distorted segregation was observed for seven (50%) polymorphic loci among monoploids derived from an interspecific hybrid. Similar distortion was observed for only one of five loci that could be contrasted between the two monoploid families. Segregation distortion was less common in the sexually derived backcross population between the interspecific hybrid and either of its parents. One locus could be putatively linked to a lethal allele because it showed distorted segregation in both monoploid families, a group of 70 heterozygous diploids derived from unreduced gametes through anther culture, and a backcross population. These diploids were used to map the polymorphic SSR markers with respect to the centromeres using half-tetrad analysis. The majority of the SSR loci mapped more than 33 cM from the centromere, suggesting the occurrence of a single crossover per chromosome arm. PMID:11962620

  7. Mutiscale Modeling of Segregation in Granular Flows

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jin [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Modeling and simulation of segregation phenomena in granular flows are investigated. Computational models at different scales ranging from particle level (microscale) to continuum level (macroscale) are employed in order to determine the important microscale physics relevant to macroscale modeling. The capability of a multi-fluid model to capture segregation caused by density difference is demonstrated by simulating grain-chaff biomass flows in a laboratory-scale air column and in a combine harvester. The multi-fluid model treats gas and solid phases as interpenetrating continua in an Eulerian frame. This model is further improved by incorporating particle rotation using kinetic theory for rapid granular flow of slightly frictional spheres. A simplified model is implemented without changing the current kinetic theory framework by introducing an effective coefficient of restitution to account for additional energy dissipation due to frictional collisions. The accuracy of predicting segregation rate in a gas-fluidized bed is improved by the implementation. This result indicates that particle rotation is important microscopic physics to be incorporated into the hydrodynamic model. Segregation of a large particle in a dense granular bed of small particles under vertical. vibration is studied using molecular dynamics simulations. Wall friction is identified as a necessary condition for the segregation. Large-scale force networks bearing larger-than-average forces are found with the presence of wall friction. The role of force networks in assisting rising of the large particle is analyzed. Single-point force distribution and two-point spatial force correlation are computed. The results show the heterogeneity of forces and a short-range correlation. The short correlation length implies that even dense granular flows may admit local constitutive relations. A modified minimum spanning tree (MST) algorithm is developed to asymptotically recover the force statistics in the

  8. Inheritance of a Chromosome 3 and 21 Translocation in the Fetuses, with One also Having Trisomy 21, in Three Pregnancies in One Family.

    Science.gov (United States)

    Pazarbasi, A; Demirhan, O; Alptekin, D; Ozgunen, Ft; Ozpak, L; Yilmaz, Mb; Nazlican, E; Tanriverdi, N; Luleyap, U; Gümürdülü, D

    2013-12-01

    The majority of chromosome rearrangements are balanced reciprocal and Robertsonian translocations. It is now known that such abnormalities cause no phenotypic effect on the carrier but lead to increased risk of producing unbalanced gametes. Here, we report the inheritance of a translocation between chromosomes 3 and 21 in a family with one of two fetuses with Down Syndrome carrying the same translocation and the other also carrying the same translocation without the additional chromosome 21. Chromosomal analysis from fetal amniotic fluid and peripheral blood lymphocytes from the family were performed at the Çukurova University Hospital at Adana, Turkey. We assessed a family in which the translocation between chromosomes 3 and 21 segregates: one of the three progenies carried the 47,XX,+21,t(3;21)(q21;q22) karyotype and presented with Down Syndrome; another of the three progenies carried the 46,XX,t(3;21) (q21;q22) karyotype and the third had the 46,XY karyotype. Their mother is phenotypically normal. Apparently this rearrangement occurred due to an unbalanced chromosome segregation of the mother [t(3;21)(q21;q22)mat]. This family will enable us to explain the behavior of segregation patterns and the mechanism for each type of translocation from carrier to carrier and their effects on reproduction and numerical aberrations. These findings can be used in clinical genetics and may be used as an effective tool for reproductive guidance and genetic counseling. PMID:24778571

  9. Novel ATRX gene damaging missense mutation c.6740A>C segregates with profound to severe intellectual deficiency without alpha thalassaemia

    Directory of Open Access Journals (Sweden)

    Habib Bouazzi

    2016-01-01

    Interpretation & conclusions: The novel mutation c.6740A>C was identified within the ATRX gene helicase domain and confirmed by Sanger sequencing in the three affected males as well as in the mother and her two daughters. This mutation was predicted to be damaging and deleterious. The novel mutation segregated with the phenotype without alpha-thalassaemia and with non-skewed X chromosome.

  10. Genetics of dioecy and causal sex chromosomes in plants

    Indian Academy of Sciences (India)

    Sushil Kumar; Renu Kumari; Vishakha Sharma

    2014-04-01

    Dioecy (separate male and female individuals) ensures outcrossing and is more prevalent in animals than in plants. Although it is common in bryophytes and gymnosperms, only 5% of angiosperms are dioecious. In dioecious higher plants, flowers borne on male and female individuals are, respectively deficient in functional gynoecium and androecium. Dioecy is inherited via three sex chromosome systems: XX/XY, XX/X0 and WZ/ZZ, such that XX or WZ is female and XY, X0 or ZZ are males. The XX/XY system generates the rarer XX/X0 andWZ/ZZ systems. An autosome pair begets XY chromosomes. A recessive loss-of-androecium mutation (ana) creates X chromosome and a dominant gynoecium-suppressing (GYS) mutation creates Y chromosome. The ana/ANA and gys/GYS loci are in the sex-determining region (SDR) of the XY pair. Accumulation of inversions, deleterious mutations and repeat elements, especially transposons, in the SDR of Y suppresses recombination between X and Y in SDR, making Y labile and increasingly degenerate and heteromorphic from X. Continued recombination between X and Y in their pseudoautosomal region located at the ends of chromosomal arms allows survival of the degenerated Y and of the species. Dioecy is presumably a component of the evolutionary cycle for the origin of new species. Inbred hermaphrodite species assume dioecy. Later they suffer degenerate-Y-led population regression. Cross-hybridization between such extinguishing species and heterologous species, followed by genome duplication of segregants from hybrids, give rise to new species.

  11. Intraspecific chromosome variability

    Directory of Open Access Journals (Sweden)

    N Dubinin

    2010-12-01

    Full Text Available (Editorial preface. The publication is presented in order to remind us of one of dramatic pages of the history of genetics. It re-opens for the contemporary reader a comprehensive work marking the priority change from plant cytogenetics to animal cytogenetics led by wide population studies which were conducted on Drosophila polytene chromosomes. The year of the publication (1937 became the point of irretrievable branching between the directions of Old World and New World genetics connected with the problems of chromosome variability and its significance for the evolution of the species. The famous book of T. Dobzhansky (1937 was published by Columbia University in the US under the title “Genetics and the origin of species”, and in the shadow of this American ‘skybuilding’ all other works grew dim. It is remarkable that both Dobzhansky and Dubinin come to similar conclusions about the role of chromosomes in speciation. This is not surprising given that they both might be considered as representatives of the Russian genetic school, by their birth and education. Interestingly, Dobzhansky had never referred to the full paper of Dubinin et al. (1937, though a previous short communication in Nature (1936 was included together with all former papers on the related subject. In full, the volume of the original publication printed in the Biological Journal in Moscow comprised 47 pages, in that number 41 pages of the Russian text accompanied by 16 Figs, a table and reference list, and, above all, 6 pages of the English summary. This final part in English is now reproduced in the authors’ version with the only addition being the reference list in the originally printed form.

  12. Familial predisposition to Wilms' tumour does not map to the short arm of chromosome 11.

    Science.gov (United States)

    Grundy, P; Koufos, A; Morgan, K; Li, F P; Meadows, A T; Cavenee, W K

    1988-11-24

    Wilms' tumour of the kidney usually occurs sporadically, but can also segregate as an autosomal dominant trait with incomplete penetrance. Patients with the WAGR syndrome of aniridia, genitourinary anomalies, mental retardation and high risk of Wilms' tumour have overlapping deletions of chromosome 11p13 which has suggested a possible location for a Wilms' tumour locus. Moreover, many sporadic tumours have lost a portion of chromosome 11p. A second locus at 11p15 is implicated by association of the tumour with the Wiedemann-Beckwith syndrome and by tumour-specific losses of chromosome 11 confined to 11p15. Here we report a multipoint linkage analysis of a family segregating for Wilms' tumour, using polymorphic DNA markers mapped to chromosome 11p. The results exclude the predisposing mutation from both locations. In a second family, the 11p15 alleles lost in the tumour were derived from the affected parent, thus precluding this region as the location of the inherited mutation. These findings imply an aetiological heterogeneity for Wilms' tumour and raise questions concerning the general applicability of the carcinogenesis model that has been useful in the understanding of retinoblastoma. PMID:2848199

  13. Vapor segregation and loss in basaltic melts

    Science.gov (United States)

    Edmonds, M.; Gerlach, T.M.

    2007-01-01

    Measurements of volcanic gases at Pu'u'O??'o??, Kilauea Volcano, Hawai'i, reveal distinct degassing regimes with respect to vapor segregation and loss during effusive activity in 2004-2005. Three styles of vapor loss are distinguished by the chemical character of the emitted volcanic gases, measured by open path Fourier transform infrared spectroscopy: 1 persistent continuous gas emission, 2 gas piston events, and 3 lava spattering. Persistent continuous gas emission is associated with magma ascent and degassing beneath the crater vents, then eruption of the degassed magma from flank vents. Gas piston events are the result of static gas accumulation at depths of 400-900 m beneath Pu'u'O??'o??. A CO2-rich gas slug travels up the conduit at a few meters per second, displacing magma as it expands. Lava spattering occurs due to dynamic bubble coalescence in a column of relatively stagnant magma. The Large gas bubbles are H2O rich and are generated by open-system degassing at depths of segregation in basaltic melts, but their implications differ. Accumulation and segregation of CO2-rich vapor at depth does not deplete the melt of H2O (required to drive lava fountains near to the surface) and therefore gas piston events can occur interspersed with lava fountaining activity. Lava spattering, however, efficiently strips H2O-rich vapor from magma beneath the crater vents; the magma must then erupt effusively from vents on the flank of the cone. ?? 2007 The Geological Society of America.

  14. X chromosome inactivation: Activation of Silencing

    NARCIS (Netherlands)

    I.H. Jonkers (Iris)

    2009-01-01

    textabstractX chromosome inactivation is a process that ensures equal expression of the X chromosomes between males, which have one X and one Y chromosome, and females, which have two X chromosomes, in mammals. Females initiate inactivation of one of their two X chromosomes early during embryogenesi

  15. Chromosome Connections: Compelling Clues to Common Ancestry

    Science.gov (United States)

    Flammer, Larry

    2013-01-01

    Students compare banding patterns on hominid chromosomes and see striking evidence of their common ancestry. To test this, human chromosome no. 2 is matched with two shorter chimpanzee chromosomes, leading to the hypothesis that human chromosome 2 resulted from the fusion of the two shorter chromosomes. Students test that hypothesis by looking for…

  16. X-chromosome workshop.

    Science.gov (United States)

    Paterson, A D

    1998-01-01

    Researchers presented results of ongoing research to the X-chromosome workshop of the Fifth World Congress on Psychiatric Genetics, covering a wide range of disorders: X-linked infantile spasms; a complex phenotype associated with deletions of Xp11; male homosexuality; degree of handedness; bipolar affective disorder; schizophrenia; childhood onset psychosis; and autism. This report summarizes the presentations, as well as reviewing previous studies. The focus of this report is on linkage findings for schizophrenia and bipolar disorder from a number of groups. For schizophrenia, low positive lod scores were obtained for markers DXS991 and DXS993 from two studies, although the sharing of alleles was greatest from brother-brother pairs in one study, and sister-sister in the other. Data from the Irish schizophrenia study was also submitted, with no strong evidence for linkage on the X chromosome. For bipolar disease, following the report of a Finnish family linked to Xq24-q27, the Columbia group reported some positive results for this region from 57 families, however, another group found no evidence for linkage to this region. Of interest, is the clustering of low positive linkage results that point to regions for possible further study. PMID:9686435

  17. Potential donor segregation to promote blood donation.

    Science.gov (United States)

    Martín-Santana, Josefa D; Beerli-Palacio, Asunción

    2008-04-01

    This work is set in the field of social marketing and more specifically in the context of blood donation. Its principal objective focuses on segregating potential donors by using the inhibitors or barriers to a blood donation behaviour as criteria. Moreover, an analysis of the predisposition to donate blood, the intrinsic and extrinsic motivations for donating blood, and the incentives that may stimulate their donation conduct was conducted for each of the four identified groups. The results reveal that the four segments differ significantly in their predisposition to donate, in their motivations and in the incentives that encourage them to donate blood. PMID:18343199

  18. Computing the complexity for Schelling segregation models

    Science.gov (United States)

    Gerhold, Stefan; Glebsky, Lev; Schneider, Carsten; Weiss, Howard; Zimmermann, Burkhard

    2008-12-01

    The Schelling segregation models are "agent based" population models, where individual members of the population (agents) interact directly with other agents and move in space and time. In this note we study one-dimensional Schelling population models as finite dynamical systems. We define a natural notion of entropy which measures the complexity of the family of these dynamical systems. The entropy counts the asymptotic growth rate of the number of limit states. We find formulas and deduce precise asymptotics for the number of limit states, which enable us to explicitly compute the entropy.

  19. Surface segregation in HAYNES 230 alloy

    International Nuclear Information System (INIS)

    The surface segregation in the Ni-based alloy HAYNES 230 was studied by Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy between 400 and 1100 deg. C. The qualitative variations of the surface contents of S, P, W, Mo, N, Si, and Mn were determined as a function of annealing temperature and time. It was found that at 925 deg. C the maximum coverage of sulphur at the alloy surface is in the range 0.06-0.15 monolayers. Chromium evaporation from the HAYNES 230 surface under UHV conditions is clearly evidenced for annealing at 1100 deg. C

  20. Surface segregation in HAYNES 230 alloy

    Science.gov (United States)

    Pop, D.; Wolski, K.

    2006-12-01

    The surface segregation in the Ni-based alloy HAYNES 230 was studied by Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy between 400 and 1100 °C. The qualitative variations of the surface contents of S, P, W, Mo, N, Si, and Mn were determined as a function of annealing temperature and time. It was found that at 925 °C the maximum coverage of sulphur at the alloy surface is in the range 0.06-0.15 monolayers. Chromium evaporation from the HAYNES 230 surface under UHV conditions is clearly evidenced for annealing at 1100 °C.

  1. Racial Segregation and the American Foreclosure Crisis

    OpenAIRE

    Rugh, Jacob S.; Massey, Douglas S.

    2010-01-01

    Although the rise in subprime lending and the ensuing wave of foreclosures was partly a result of market forces that have been well-identified in the literature, in the United States it was also a highly racialized process. We argue that residential segregation created a unique niche of poor minority clients who were differentially marketed risky subprime loans that were in great demand for use in mortgage-backed securities that could be sold on secondary markets. We test this argument by reg...

  2. Isothermal Gravitational Segregation: Algorithms and Specifications

    DEFF Research Database (Denmark)

    Halldórsson, Snorri; Stenby, Erling Halfdan

    2000-01-01

    New algorithms for calculating the isothermal equilibrium state of reservoir fluids under the influence of gravity are presented. Two types of specifications are considered: the specification of pressure and composition at a reference depth; and the specification of the total overall content...... of the reservoir, along with the reservoir geometry. It is shown how both types of calculations can be performed in an efficient and robust manner using volume-based thermodynamics. The new method makes it possible to evaluate the influence of reservoir geometry and gravity segregation on the hydrocarbon reserves...

  3. mars and tousled-like kinase act in parallel to ensure chromosome fidelity in Drosophila

    Directory of Open Access Journals (Sweden)

    Huang Hsiao-Yu

    2009-06-01

    Full Text Available Abstract Background High levels of Hepatoma Up-Regulated Protein (HURP and Tousled-Like Kinase (TLK transcripts are found in hepatocellular carcinoma. HURP overexpression induces anchorage-independent growth of 293-T cells and enhances a rough-eye phenotype resulting from tlk overexpression in Drosophila. In addition, both HURP and Mars, a Drosophila HURP sequence homologue, promote polymerization of mitotic spindles. Thus, the genetic interaction of mars with tlk might be required for accurate chromosome segregation. Methods To reveal whether chromosome fidelity was decreased, the frequency of gynandromorphy, an individual with both male and female characteristics, and of non-disjunction were measured in the progeny from parents with reduced mars and/or tlk activities and analyzed by Student's t-test. To show that the genetic interaction between mars and tlk is epistatic or parallel, a cytological analysis of embryos with either reduced or increased activities of mars and/or tlk was used to reveal defects in mitotic-spindle morphology and chromosome segregation. Results A significant but small fraction of the progeny from parents with reduced mars activity showed gynandromorphy and non-disjunction. Results of cytological analysis revealed that the decrease in chromosome fidelity was a result of delayed polymerization of the mitotic spindle, which led to asynchronous chromosome segregation in embryos that had reduced mars activity. By removing one copy of tousled-like kinase (tlk from flies with reduced mars activity, chromosome fidelity was further reduced. This was indicated by an increased in the non-disjunction rate and more severe asynchrony. However, the morphology of the mitotic spindles in the embryos at metaphase where both gene activities were reduced was similar to that in mars embryos. Furthermore, tlk overexpression did not affect the morphology of the mitotic spindles and the cellular localization of Mars protein. Conclusion

  4. Segregation and sporadic cases in families with Hunter's syndrome.

    OpenAIRE

    Machill, G; Barbujani, G.; Danieli, G A; Herrmann, F H

    1991-01-01

    Segregation analysis on five samples of families with Hunter's syndrome (158 cases overall) shows that the mutant allele segregates in agreement with Mendelian expectations for an X linked recessive disease, but the proportion of sporadic cases is significantly lower than expected under mutation-selection equilibrium. Heterogeneity among the samples is apparent, but it is caused entirely by a sample of Ashkenazi families, whose segregation pattern has previously been interpreted as supporting...

  5. Metropolitan Racial Residential Segregation and Cardiovascular Mortality: Exploring Pathways

    OpenAIRE

    Greer, Sophia; Kramer, Michael R; Cook-Smith, Jessica N.; Casper, Michele L.

    2013-01-01

    Racial residential segregation has been associated with an increased risk for heart disease and stroke deaths. However, there has been little research into the role that candidate mediating pathways may play in the relationship between segregation and heart disease or stroke deaths. In this study, we examined the relationship between metropolitan statistical area (MSA)-level segregation and heart disease and stroke mortality rates, by age and race, and also estimated the effects of various ed...

  6. The impact of fiscal decentralization on income segregation

    OpenAIRE

    Francisco Martínez Mora

    2004-01-01

    We investigate how decentralizing the provision and funding of a publicly provided good from central (or regional) to local governments affects income segregation in an urban area. As the previous theoretical literature suggests, local provision and funding of a publicly provided good by itself generates incentives for income segregation. However, other segregating forces such as local amenities are also at work in urban areas. We show that, once this important feature of urban economies is c...

  7. Evaluating segregation in HSLA steels using computational thermodynamics

    OpenAIRE

    Meire Guimarães Lage; André Luiz Vasconcellos da Costa e Silva

    2015-01-01

    A low level of segregation in high strength steel plates used to manufacture large diameter pipes is important for the performance of these materials in sour environments. In this work, the level of segregation of different HSLA steels was assessed by computational thermodynamics to identify the most promising compositions. Equilibrium phase diagrams and mass fraction of solid phase diagrams were used to quantify the segregation at the end of solidification. It was verified from the results t...

  8. Housing Tenure and Residential Segregation in Metropolitan America

    OpenAIRE

    Friedman, Samantha; Tsao, Hui-shien; Chen, Cheng

    2013-01-01

    Homeownership, a symbol of the American dream, is one of the primary ways through which families accumulate wealth, particularly for blacks and Hispanics. Surprisingly, no study has explicitly documented the segregation of minority owners and renters from whites. Using data from Census 2000, this study aims to fill this gap. Analyses here reveal that the segregation of black renters relative to whites is significantly lower than the segregation of black owners from whites, controlling for rel...

  9. Racial/ethnic residential segregation and cardiovascular disease risk

    OpenAIRE

    Kershaw, Kiarri N.; Albrecht, Sandra S.

    2015-01-01

    A growing body of research has examined whether racial/ethnic residential segregation contributes to health disparities, but recent findings in the literature, particularly with respect to cardiovascular disease (CVD) risk, have not been summarized. This review provides an overview of findings from studies of racial/ethnic residential segregation of non-Hispanic blacks and Hispanics with CVD risk published between January 2011 and July 2014. The majority of studies of black segregation showed...

  10. Residential Segregation and Immigrants' Satisfaction with the Neighborhood in Germany

    OpenAIRE

    Dill, Verena; Jirjahn, Uwe; Tsertsvadze, Georgi

    2011-01-01

    Using data from the German Socio-Economic Panel, this study examines the relationship between immigrant residential segregation and immigrants' satisfaction with the neighborhood. The estimates show that immigrants living in segregated areas are less satisfied with the neighborhood. This is consistent with the hypothesis that housing discrimination rather than self-selection plays an important role in immigrant residential segregation. Our result holds true even when controlling for other inf...

  11. Residential Segregation of Socioeconomic Variables and Health Indices in Iran

    OpenAIRE

    Seyed Saeed Hashemi Nazari; Mahmood Mahmoodi; Kourosh Holakouie Naieni

    2013-01-01

    Background: Measures of segregation are essential tools for evaluation of social equality. They describe complex structural patterns by single quantities and allow the comparison of inequalities over time or between residential places. In many countries, patterns of residential segregation are well described (e.g., South Africa, Great Britain, United States of America). In this study, for the first time in Iran, we measured residential segregation for some socioeconomic and health variables a...

  12. Segregation in Vertically Vibrated Binary Granular Mixtures with Same Size

    Institute of Scientific and Technical Information of China (English)

    SHI Qing-Fan; SUN Gang; HOU Mei-Ying; LU Kun-Quan

    2006-01-01

    @@ Segregation in vertically vibrated binary granular mixtures with same size is studied experimentally. A new partial segregated state is found in this system. This state exists between the completely mixed state and the pure segregated state, and has the characteristic that the lighter particles tend to rise and form a pure layer on the top of the system while the heavier particles and some of the lighter ones stay at the bottom and form a mixed layer.

  13. Segregation or Integration? Immigrant Self-Employment in Switzerland

    OpenAIRE

    Juhasz Liebermann, Anne; Suter, Christian; Iglesias, Katia

    2016-01-01

    This article investigates whether immigrant self-employment is related more to segregation in the labour market than work as an employee (making it justifiable to speak of ethnic business) or whether, on the contrary, it reflects equality with the self-employment by the Swiss. The distinctive features of this research design are the comparison of ethnic segregation in the labour market with gender-specific segregation and the fact that, apart from migrants of the first generation, members of ...

  14. Factors Influencing Occupational Segregation by Gender in Malaysia

    OpenAIRE

    Noor Rahamah Abu Bakar

    2014-01-01

    In many developing countries, occupational segregation by gender is a topic that is much discussed but very few researches had been carried out. In Malaysia, secondary sources of data, such as the Population and Housing Census reports and Social Statistics Bulletins of the Malaysian Statistics Department do show that there have been some changes in the general trends of occupational segregation in the country but factual details of occupational segregation based on gender are rather scanty. T...

  15. Causes of Educational Segregation in Sweden--School Choice or Residential Segregation

    Science.gov (United States)

    Yang Hansen, Kajsa; Gustafsson, Jan-Eric

    2016-01-01

    The aims of the study were to examine changes in school segregation across different types of municipalities between 1998 and 2011 in Sweden, and to explore the extent to which these changes are the consequences of school choice. Multilevel models were applied to register data using a counterfactual approach. The results showed that school…

  16. Mapping School Segregation: Using GIS to Explore Racial Segregation between Schools and Their Corresponding Attendance Areas

    Science.gov (United States)

    Sohoni, Deenesh; Saporito, Salvatore

    2009-01-01

    We examine whether student enrollment in nonneighborhood schools changes levels of racial segregation in public schools across urban school districts by comparing the racial composition of schools and their corresponding attendance area. This comparison was made possible by using geographic information systems (GIS) to link maps of elementary,…

  17. The Aurora B kinase in chromosome biorientation and spindle checkpoint signalling

    Directory of Open Access Journals (Sweden)

    Veronica eKrenn

    2015-10-01

    Full Text Available Aurora B, a member of the Aurora family of serine/threonine protein kinases, is a key player in chromosome segregation. As part of a macromolecular complex known as the chromosome passenger complex, Aurora B concentrates early during mitosis in the proximity of centromeres and kinetochores, the sites of attachment of chromosomes to spindle microtubules. There, it contributes to a number of processes that impart fidelity to cell division, including kinetochore stabilization, kinetochore-microtubule attachment, and the regulation of a surveillance mechanism named the spindle assembly checkpoint. In the regulation of these processes, Aurora B is the fulcrum of a remarkably complex network of interactions that feed back on its localization and activation state. In this review we discuss the multiple roles of Aurora B during mitosis, focusing in particular on its role at centromeres and kinetochores. Many details of the network of interactions at these locations remain poorly understood, and we focus here on several crucial outstanding questions.

  18. Epigenetic Histone Marks of Extended Meta-Polycentric Centromeres of Lathyrus and Pisum Chromosomes.

    Science.gov (United States)

    Neumann, Pavel; Schubert, Veit; Fuková, Iva; Manning, Jasper E; Houben, Andreas; Macas, Jiří

    2016-01-01

    Species of the legume genera Lathyrus and Pisum possess chromosomes that exhibit a unique structure of their centromeric regions, which is clearly apparent during metaphase by the formation of extended primary constrictions which span up to a third of the length of the chromosome. In addition, these species express two different variants of the CenH3 protein which are co-localized in multiple domains along the poleward surface of the primary constrictions. Here, we show that the constrictions represent a distinct type of chromatin differing from the chromosome arms. In metaphase, histone phosphorylation patterns including H3S10ph, H3S28ph, and H3T3ph were observed along the entire constriction, in a way similar to holocentric chromosomes. On the other hand, distribution of phosphorylated H2AT120 was different from that previously reported from either, holocentric and monocentric chromosomes, occurring at chromatin surrounding but not overlapping CenH3 domains. Since some of these phosphorylations play a role in chromatid cohesion, it can be assumed that they facilitate correct chromosome segregation by ensuring that multiple separate CenH3 domains present on the same chromatid are oriented toward the same pole. The constrictions also displayed distinct patterns of histone methylation marks, being enriched in H3K9me2 and depleted in H3K4me3 and H3K27me2 compared to the chromosome arms. Super-resolution fluorescence microscopy revealed that although both CenH3 protein variants are present in all CenH3 domains detected on metaphase chromosomes, they are only partially co-localized while there are chromatin subdomains which are mostly made of only one CenH3 variant. Taken together, these data revealed specific features of extended primary constrictions of Lathyrus and Pisum and support the idea that they may represent an intermediate stage between monocentric and holocentric chromosomes. PMID:26973677

  19. Epigenetic histone marks of extended meta-polycentric centromeres of Lathyrus and Pisum chromosomes

    Directory of Open Access Journals (Sweden)

    Pavel eNeumann

    2016-03-01

    Full Text Available Species of the legume genera Lathyrus and Pisum possess chromosomes that exhibit a unique structure of their centromeric regions, which is clearly apparent during metaphase by the formation of extended primary constrictions which span up to a third of the length of the chromosome. In addition, these species express two different variants of the CenH3 protein which are co-localized in multiple domains along the poleward surface of the primary constrictions. Here we show that the constrictions represent a distinct type of chromatin differing from the chromosome arms. In metaphase, histone phosphorylation patterns including H3S10ph, H3S28ph and H3T3ph were observed along the entire constriction, in a way similar to holocentric chromosomes. On the other hand, distribution of phosphorylated H2AT120 was different from that previously reported from either, holocentric and monocentric chromosomes, occurring at chromatin surrounding but not overlapping CenH3 domains. Since some of these phosphorylations play a role in chromatid cohesion, it can be assumed that they facilitate correct chromosome segregation by ensuring that multiple separate CenH3 domains present on the same chromatid are oriented towards the same pole. The constrictions also displayed distinct patterns of histone methylation marks, being enriched in H3K9me2 and depleted in H3K4me3 and H3K27me2 compared to the chromosome arms. High resolution fluorescence microscopy revealed that although both CenH3 protein variants are present in all CenH3 domains detected on metaphase chromosomes, they are only partially co-localized while there are chromatin subdomains which are mostly made of only one CenH3 variant. Taken together, these data revealed specific features of extended primary constrictions of Lathyrus and Pisum and support the idea that they may represent an intermediate stage between monocentric and holocentric chromosomes.

  20. Grain boundary segregation and intergranular fracture in molybdenum

    International Nuclear Information System (INIS)

    The present paper reports results from a systematic study of segregation and intergranular embrittlement in binary molybdenum-oxygen and ternary molybdenum-oxygen-carbon alloys. The experiments were carried out on 'bamboo' specimens containing a series of identical single grain boundaries traversing their cross-sections. Measurements have been made of the activation energy for oxygen segregation to grain boundaries in the binary alloys. The influence of carbon additions on the level of oxygen segregation and the influence of oxygen segregation on the energy to fracture have been studied. Results from metallographic studies show the effects of segregation on fracture surface topography and dislocation surfaces immediately adjacent to the fracture surfaces. The thermodynamics of oxygen segregation to grain boundaries is considered and the role played by carbon in inhibiting segregation. The influence of segregation on the work of fracture is also considered and it is shown that the reduction in oxygen segregation resulting from the addition of carbon produces small increases in fracture energy. This increases the local stress to propagate a crack sufficiently to promote plastic deformation which blunts the crack tip; this reduces the stress concentration at the crack tip and the applied fracture stress and the work to fracture is thus increased. (author)

  1. Economic Residential Segregation and Educational Achievements: Evidence from Chile

    OpenAIRE

    Román, Miguel Vargas

    2012-01-01

    Using a database from Chile, we have tested empirically the effects of economic residential segregation on educational achievements. Our hypothesis is based on literature’s findings about segregation’s negative impact on individuals’ well being. We found that segregation has negative impacts. This result would have interesting policy implications and goes in the opposite directions of those investigations’ findings, which indicate that segregation has just negligible effects. Keywords...

  2. Occupational sex segregation and working time: Regional evidence from Germany

    Directory of Open Access Journals (Sweden)

    Humpert Stephan

    2014-01-01

    Full Text Available This paper provides descriptive evidence for declining occupational sex segregation on the German labor market, especially concerning the regional differences between the former East and West Germany. I use segregation measures and long-run social security data for the decade of 1992 to 2004. While segregation has declined over time, it remains higher for the eastern part of Germany. Although this finding is observable for full-time and part-time work, segregation is always lower in part-time employment.

  3. Requirements for the evaluation of computational speech segregation systems.

    Science.gov (United States)

    May, Tobias; Dau, Torsten

    2014-12-01

    Recent studies on computational speech segregation reported improved speech intelligibility in noise when estimating and applying an ideal binary mask with supervised learning algorithms. However, an important requirement for such systems in technical applications is their robustness to acoustic conditions not considered during training. This study demonstrates that the spectro-temporal noise variations that occur during training and testing determine the achievable segregation performance. In particular, such variations strongly affect the identification of acoustical features in the system associated with perceptual attributes in speech segregation. The results could help establish a framework for a systematic evaluation of future segregation systems.

  4. Requirements for the evaluation of computational speech segregation systems

    DEFF Research Database (Denmark)

    May, Tobias; Dau, Torsten

    2014-01-01

    Recent studies on computational speech segregation reported improved speech intelligibility in noise when estimating and applying an ideal binary mask with supervised learning algorithms. However, an important requirement for such systems in technical applications is their robustness to acoustic...... conditions not considered during training. This study demonstrates that the spectro-temporal noise variations that occur during training and testing determine the achievable segregation performance. In particular, such variations strongly affect the identification of acoustical features in the system...... associated with perceptual attributes in speech segregation. The results could help establish a framework for a systematic evaluation of future segregation systems....

  5. Causes of oncogenic chromosomal translocation

    OpenAIRE

    Aplan, Peter D.

    2005-01-01

    Non-random chromosomal translocations are frequently associated with a variety of cancers, especially hematologic malignancies and childhood sarcomas In addition to their diagnostic utility, chromosomal translocations are increasingly being used in the clinic to guide therapeutic decisions. However, the mechanisms which cause these translocations remain poorly understood. Illegit...

  6. Cohesin in determining chromosome architecture

    Energy Technology Data Exchange (ETDEWEB)

    Haering, Christian H., E-mail: christian.haering@embl.de [Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Heidelberg (Germany); Jessberger, Rolf, E-mail: rolf.jessberger@tu-dresden.de [Institute of Physiological Chemistry, Dresden University of Technology, Dresden (Germany)

    2012-07-15

    Cells use ring-like structured protein complexes for various tasks in DNA dynamics. The tripartite cohesin ring is particularly suited to determine chromosome architecture, for it is large and dynamic, may acquire different forms, and is involved in several distinct nuclear processes. This review focuses on cohesin's role in structuring chromosomes during mitotic and meiotic cell divisions and during interphase.

  7. Genetic mapping shows intraspecific variation and transgressive segregation for caterpillar-induced aphid resistance in maize.

    Science.gov (United States)

    Tzin, Vered; Lindsay, Penelope L; Christensen, Shawn A; Meihls, Lisa N; Blue, Levi B; Jander, Georg

    2015-11-01

    Plants in nature have inducible defences that sometimes lead to targeted resistance against particular herbivores, but susceptibility to others. The metabolic diversity and genetic resources available for maize (Zea mays) make this a suitable system for a mechanistic study of within-species variation in such plant-mediated interactions between herbivores. Beet armyworms (Spodoptera exigua) and corn leaf aphids (Rhopalosiphum maidis) are two naturally occurring maize herbivores with different feeding habits. Whereas chewing herbivore-induced methylation of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc) to form 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) promotes caterpillar resistance, lower DIMBOA-Glc levels favour aphid reproduction. Thus, caterpillar-induced DIMBOA-Glc methyltransferase activity in maize is predicted to promote aphid growth. To test this hypothesis, the impact of S. exigua feeding on R. maidis progeny production was assessed using seventeen genetically diverse maize inbred lines. Whereas aphid progeny production was increased by prior caterpillar feeding on lines B73, Ki11, Ki3 and Tx303, it decreased on lines Ky21, CML103, Mo18W and W22. Genetic mapping of this trait in a population of B73 × Ky21 recombinant inbred lines identified significant quantitative trait loci on maize chromosomes 1, 7 and 10. There is a transgressive segregation for aphid resistance, with the Ky21 alleles on chromosomes 1 and 7 and the B73 allele on chromosome 10 increasing aphid progeny production. The chromosome 1 QTL coincides with a cluster of three maize genes encoding benzoxazinoid O-methyltransferases that convert DIMBOA-Glc to HDMBOA-Glc. Gene expression studies and benzoxazinoid measurements indicate that S. exigua -induced responses in this pathway differentially affect R. maidis resistance in B73 and Ky21. PMID:26462033

  8. Highly Nonlinear Ising Model and Social Segregation

    CERN Document Server

    Sumour, M A; Shabat, M M

    2011-01-01

    The usual interaction energy of the random field Ising model in statistical physics is modified by complementing the random field by added to the energy of the usual Ising model a nonlinear term S^n were S is the sum of the neighbor spins, and n=0,1,3,5,7,9,11. Within the Schelling model of urban segregation, this modification corresponds to housing prices depending on the immediate neighborhood. Simulations at different temperatures, lattice size, magnetic field, number of neighbors and different time intervals showed that results for all n are similar, expect for n=3 in violation of the universality principle and the law of corresponding states. In order to find the critical temperatures, for large n we no longer start with all spins parallel but instead with a random configuration, in order to facilitate spin flips. However, in all cases we have a Curie temperature with phase separation or long-range segregation only below this Curie temperature, and it is approximated by a simple formula: Tc is proportion...

  9. Wilhelm Weinberg's early contribution to segregation analysis.

    Science.gov (United States)

    Stark, Alan; Seneta, Eugene

    2013-09-01

    Wilhelm Weinberg (1862-1937) is a largely forgotten pioneer of human and medical genetics. His name is linked with that of the English mathematician G. H. Hardy in the Hardy-Weinberg law, pervasive in textbooks on population genetics since it expresses stability over generations of zygote frequencies AA, Aa, aa under random mating. One of Weinberg's signal contributions, in an article whose centenary we celebrate, was to verify that Mendel's segregation law still held in the setting of human heredity, contrary to the then-prevailing view of William Bateson (1861-1926), the leading Mendelian geneticist of the time. Specifically, Weinberg verified that the proportion of recessive offspring genotypes aa in human parental crossings Aa × Aa (that is, the segregation ratio for such a setting) was indeed p=1/4. We focus in a nontechnical way on his procedure, called the simple sib method, and on the heated controversy with Felix Bernstein (1878-1956) in the 1920s and 1930s over work stimulated by Weinberg's article. PMID:24018765

  10. Decentralization as a Cause of Spatial Segregation

    Directory of Open Access Journals (Sweden)

    Jasarovic Ema Alihodzic

    2016-01-01

    Full Text Available City represents an incomplete dynamic process prone to the expansion with a causal link between urban expansion and socio-spatial segregation. The socio-spatial distribution in the city is mostly related to the increased social polarization and inequality. There is a clear connection between divided society and divided city: if society is divided, urban space must be divided. It is the question of the relations between the social inequalities on one hand, and spatial segregation on the other. In the last 10 years, Podgorica is the city that shows alarming statistic values when it comes to demographic trends and the influx of the residents from the northern municipalities, which necessarily causes the city sprawl. Past experiences show that city is unevenly expanding, creating new functions and zones expressed by socio-spatial differences. The beginning of this process lies in modernist conception of the city, by which city was mostly developed, while the current functional organization is based on the same concept. With the first urban plans, which carried similarproblems mentioned in previous section, Podgorica was divided into three clearly differentiated zones: Stara Varoš, Nova Varoš and Novi grad, which became a platform for hierarchical divisions within the space, reflecting them in the society.

  11. SOCIAL POLARIZATION AND SEGREGATION IN BEIJING

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The biggest change in Beijing during the last decade has been in its social structure. This transition is changing the existing situation of social "equality", and leads to polarization both in individual communities and in society as a whole. As a result, social variations and conflicting interest are growing, and some new social groups are emerging. In this paper we seek to explore a new urban phenomenon in post-1984 Beijing: social polarization and segregation. At first, we will discuss some elements explaining social polarization. The elements and the processes can be traced back to two main aspects of the economic reforms, namely the internal reforms unleashing a huge rural exodus and the open door policy. Special attention will be paid to the new lower end of the social ladder, which is made up largely by rural migrantsthat make up the so-called floating population.Finally we will explore how these social changes translate into urban segregation, with some consideration for future develop-ments.

  12. Comparative genetic mapping points to different sex chromosomes in sibling species of wild strawberry (Fragaria).

    Science.gov (United States)

    Goldberg, Margot T; Spigler, Rachel B; Ashman, Tia-Lynn

    2010-12-01

    Separate sexes have evolved repeatedly from hermaphroditic ancestors in flowering plants, and thus select taxa can provide unparalleled insight into the evolutionary dynamics of sex chromosomes that are thought to be shared by plants and animals alike. Here we ask whether two octoploid sibling species of wild strawberry--one almost exclusively dioecious (males and females), Fragaria chiloensis, and one subdioecious (males, females, and hermaphrodites), F. virginiana--share the same sex-determining chromosome. We created a genetic map of the sex chromosome and its homeologs in F. chiloensis and assessed macrosynteny between it and published maps of the proto-sex chromosome of F. virginiana and the homeologous autosome of hermaphroditic diploid species. Segregation of male and female function in our F. chiloensis mapping population confirmed that linkage and dominance relations are similar to those in F. virginiana. However, identification of the molecular markers most tightly linked to the sex-determining locus in the two octoploid species shows that, in both, this region maps to homeologues of chromosome 6 in diploid congeners, but is located at opposite ends of their respective chromosomes.

  13. Three decades of studies on chromosomal polymorphism of Drosophila willistoni and description of fifty different rearrangements

    Directory of Open Access Journals (Sweden)

    Claudia Rohde

    2012-01-01

    Full Text Available Drosophila willistoni (Insecta, Diptera is considered a paradigm for evolutionary studies. Their chromosomes are characterized by multiple paracentric inversions that make it hard to identify and describe chromosomal poly-morphisms. In the present report we attempted to systematize the description of all the 50 inversions found in the last three decades, since we have been studying the chromosomes of several individuals of 30 different populations, including the one used in the genome sequencing project (Gd-H4-1. We present the photographic register of 11 arrangements in the left arm of the X chromosome (XL, eight in the right arm (XR, 10 in the left arm of chromosome II (IIL, eight in its right arm (IIR and 13 in chromosome III. This information also includes their breakpoints on the reference photomap. A clear geographic difference was detected in XL and XR, with different fixed arrangements depending on the origin of the population studied. Through the comparison of all X arrangements it was possible to infer the putative ancestral arrangements, i.e., those related to all the remaining arrangements through the small number of inversions that occurred in the past, which we will call XL-A and XR-A. In the autosomes (IIL/IIR and III, fixed inversions were detected, but most are segregating in different frequencies along the geographical distribution of the D. willistoni populations.

  14. Genetics Home Reference: ring chromosome 20 syndrome

    Science.gov (United States)

    ... 3 links) Encyclopedia: Chromosome Encyclopedia: Epilepsy Health Topic: Epilepsy Genetic and Rare Diseases Information Center (1 link) Ring chromosome 20 Additional NIH Resources (2 links) National Human Genome Research Institute: Chromosome Abnormalities National Institute of ...

  15. Genetics Home Reference: ring chromosome 14 syndrome

    Science.gov (United States)

    ... Encyclopedia: Chromosome Health Topic: Developmental Disabilities Health Topic: Epilepsy Genetic and Rare Diseases Information Center (1 link) Ring chromosome 14 Additional NIH Resources (2 links) National Human Genome Research Institute: Chromosome Abnormalities National Institute of ...

  16. Higher order structure of chromosomes.

    Science.gov (United States)

    Okada, T A; Comings, D E

    1979-04-01

    Isolated Chinese hamster metaphase chromosomes were resuspended in 4 M ammonium acetate and spread on a surface of distilled water or 0.15 to 0.5 M ammonium acetate. The DNA was released in the form of a regular series of rosettes connected by interrossette DNA. The mean length of the rosette DNA was 14 micron, similar to the mean length of 10 micron for chromomere DNA of Drosophila polytene chromosomes. The mean interrosette DNA was 4.2 micron. SDS gel electrophoresis of the chromosomal nonhistone proteins showed them to be very similar to nuclear nonhistone proteins except for the presence of more actin and tubulin. Nuclear matrix proteins were present in the chromosomes and may play a role in forming the rosettes. Evidence that the rosette pattern is artifactual versus the possibility that it represents a real organizational substructure of the chromosomes is reviewed.

  17. ADN et chromosomes

    OpenAIRE

    Hayes, Hélène

    2000-01-01

    Chaque chromosome contient une seule molécule d’ADN. L’ADN déroulé d’un noyau de cellule humaine mesurerait environ 1,8 m : chaque molécule d’ADN est enroulée et compactée en plusieurs étapes, grâce à l’association de différentes protéines, et loge dans le noyau de 6 µm de diamètre. Le degré de condensation de l’ADN est variable selon les régions chromosomiques et les régions les moins condensées sont les plus riches en gènes. L’ADN est composé d’une variété de séquences codantes ou non et ré...

  18. Schizophrenia and chromosomal deletions

    Energy Technology Data Exchange (ETDEWEB)

    Lindsay, E.A.; Baldini, A. [Baylor College of Medicine, Houston, TX (United States); Morris, M. A. [Univ. of Geneva School of Medicine, NY (United States)] [and others

    1995-06-01

    Recent genetic linkage analysis studies have suggested the presence of a schizophrenia locus on the chromosomal region 22q11-q13. Schizophrenia has also been frequently observed in patients affected with velo-cardio-facial syndrome (VCFS), a disorder frequently associated with deletions within 22q11.1. It has been hypothesized that psychosis in VCFS may be due to deletion of the catechol-o-methyl transferase gene. Prompted by these observations, we screened for 22q11 deletions in a population of 100 schizophrenics selected from the Maryland Epidemiological Sample. Our results show that there are schizophrenic patients carrying a deletion of 22q11.1 and a mild VCFS phenotype that might remain unrecognized. These findings should encourage a search for a schizophrenia-susceptibility gene within the deleted region and alert those in clinical practice to the possible presence of a mild VCFS phenotype associated with schizophrenia. 9 refs.

  19. X-Chromosome dosage compensation.

    Science.gov (United States)

    Meyer, Barbara J

    2005-01-01

    In mammals, flies, and worms, sex is determined by distinctive regulatory mechanisms that cause males (XO or XY) and females (XX) to differ in their dose of X chromosomes. In each species, an essential X chromosome-wide process called dosage compensation ensures that somatic cells of either sex express equal levels of X-linked gene products. The strategies used to achieve dosage compensation are diverse, but in all cases, specialized complexes are targeted specifically to the X chromosome(s) of only one sex to regulate transcript levels. In C. elegans, this sex-specific targeting of the dosage compensation complex (DCC) is controlled by the same developmental signal that establishes sex, the ratio of X chromosomes to sets of autosomes (X:A signal). Molecular components of this chromosome counting process have been defined. Following a common step of regulation, sex determination and dosage compensation are controlled by distinct genetic pathways. C. elegans dosage compensation is implemented by a protein complex that binds both X chromosomes of hermaphrodites to reduce transcript levels by one-half. The dosage compensation complex resembles the conserved 13S condensin complex required for both mitotic and meiotic chromosome resolution and condensation, implying the recruitment of ancient proteins to the new task of regulating gene expression. Within each C. elegans somatic cell, one of the DCC components also participates in the separate mitotic/meiotic condensin complex. Other DCC components play pivotal roles in regulating the number and distribution of crossovers during meiosis. The strategy by which C. elegans X chromosomes attract the condensin-like DCC is known. Small, well-dispersed X-recognition elements act as entry sites to recruit the dosage compensation complex and to nucleate spreading of the complex to X regions that lack recruitment sites. In this manner, a repressed chromatin state is spread in cis over short or long distances, thus establishing the

  20. Micro and Macro Segregation in Alloys Solidifying with Equiaxed Morphology

    Science.gov (United States)

    Stefanescu, Doru M.; Curreri, Peter A.; Leon-Torres, Jose; Sen, Subhayu

    1996-01-01

    To understand macro segregation formation in Al-Cu alloys, experiments were run under terrestrial gravity (1g) and under low gravity during parabolic flights (10(exp -2) g). Alloys of two different compositions (2% and 5% Cu) were solidified at two different cooling rates. Systematic microscopic and SEM observations produced microstructural and segregation maps for all samples. These maps may be used as benchmark experiments for validation of microstructure evolution and segregation models. As expected, the macro segregation maps are very complex. When segregation was measured along the central axis of the sample, the highest macro segregation for samples solidified at 1g was obtained for the lowest cooling rate. This behavior is attributed to the longer time available for natural convection and shrinkage flow to affect solute redistribution. In samples solidified under low-g, the highest macro-segregation was obtained at the highest cooling rate. In general, low-gravity solidification resulted in less segregation. To explain the experimental findings, an analytical (Flemings-Nereo) and a numerical model were used. For the numerical model, the continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the microscopic transport phenomena, for a two-phase system. The model proposed considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The Flemings-Nereo model explains well macro segregation in the initial stages of low-gravity segregation. The numerical model can describe the complex macro segregation pattern and the differences between low- and high-gravity solidification.

  1. High genetic differentiation between an African and a non-African strain of Drosophila simulans revealed by segregation distortion and reduced crossover frequency.

    Science.gov (United States)

    Tatsuta, Haruki; Takano-Shimizu, Toshiyuki

    2009-11-01

    Drosophila simulans strains originating from Madagascar and nearby islands in the Indian Ocean often differ from those elsewhere in the number of sex comb teeth and the degree of morphological anomaly in hybrids with D. melanogaster. Here, we report a strong segregation distortion in the F1 intercross between two D. simulans strains originating from Madagascar and the US, possibly at both the gametic and zygotic levels. Strong bias against alleles of the Madagascar strain was observed for all ten marker loci distributed over the entire second chromosome in the F1 intercross, but only a few showed a weak distortion in the isogenic backgrounds of either strains. Significant deviations of genotype frequencies from Hardy-Weinberg proportions were consistently observed for the second chromosome. By contrast, the X and third chromosomes did not show any strong segregation distortion. Crossover frequency on the second chromosome was uniformly reduced in isogenic backgrounds whereas the map lengths in the F1 intercross were comparable to or larger than that of the standard D. melanogaster map. We discuss these findings in relation to previous studies on other traits and interspecific differences between D. mauritiana, which is endemic to Mauritius Island, and D. simulans. PMID:19590966

  2. Chromatid Painting for Chromosomal Inversion Detection Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose the continued development of a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and...

  3. Chromatid Painting for Chromosomal Inversion Detection Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a novel approach to the detection of chromosomal inversions. Transmissible chromosome aberrations (translocations and inversions) have profound genetic...

  4. Mitotic chromosome condensation in vertebrates

    Energy Technology Data Exchange (ETDEWEB)

    Vagnarelli, Paola, E-mail: P.Vagnarelli@ed.ac.uk

    2012-07-15

    Work from several laboratories over the past 10-15 years has revealed that, within the interphase nucleus, chromosomes are organized into spatially distinct territories [T. Cremer, C. Cremer, Chromosome territories, nuclear architecture and gene regulation in mammalian cells, Nat. Rev. Genet. 2 (2001) 292-301 and T. Cremer, M. Cremer, S. Dietzel, S. Muller, I. Solovei, S. Fakan, Chromosome territories-a functional nuclear landscape, Curr. Opin. Cell Biol. 18 (2006) 307-316]. The overall compaction level and intranuclear location varies as a function of gene density for both entire chromosomes [J.A. Croft, J.M. Bridger, S. Boyle, P. Perry, P. Teague,W.A. Bickmore, Differences in the localization and morphology of chromosomes in the human nucleus, J. Cell Biol. 145 (1999) 1119-1131] and specific chromosomal regions [N.L. Mahy, P.E. Perry, S. Gilchrist, R.A. Baldock, W.A. Bickmore, Spatial organization of active and inactive genes and noncoding DNA within chromosome territories, J. Cell Biol. 157 (2002) 579-589] (Fig. 1A, A'). In prophase, when cyclin B activity reaches a high threshold, chromosome condensation occurs followed by Nuclear Envelope Breakdown (NEB) [1]. At this point vertebrate chromosomes appear as compact structures harboring an attachment point for the spindle microtubules physically recognizable as a primary constriction where the two sister chromatids are held together. The transition from an unshaped interphase chromosome to the highly structured mitotic chromosome (compare Figs. 1A and B) has fascinated researchers for several decades now; however a definite picture of how this process is achieved and regulated is not yet in our hands and it will require more investigation to comprehend the complete process. From a biochemical point of view a vertebrate mitotic chromosomes is composed of DNA, histone proteins (60%) and non-histone proteins (40%) [6]. I will discuss below what is known to date on the contribution of these two different classes

  5. Algorithms for physical segregation of coal

    Science.gov (United States)

    Ganguli, Rajive

    The capability for on-line measurement of the quality characteristics of conveyed coal now enables mine operators to take advantage of the inherent heterogeneity of those streams and split them into wash and no-wash stocks. Relative to processing the entire stream, this reduces the amount of coal that must be washed at the mine and thereby reduces processing costs, recovery losses, and refuse generation levels. In this dissertation, two classes of segregation algorithms, using time series models and moving windows are developed and demonstrated using field and simulated data. In all of the developed segregation algorithms, a "cut-off" ash value was computed for coal scanned on the running conveyor belt by the ash analyzer. It determined if the coal was sent to the wash pile or to the nowash pile. Forecasts from time series models, at various lead times ahead, were used in one class of the developed algorithms, to determine the cut-off ash levels. The time series models were updated from time to time to reflect changes in process. Statistical Process Control (SPC) techniques were used to determine if an update was necessary at a given time. When an update was deemed necessary, optimization techniques were used to determine the next best set of model parameters. In the other class of segregation algorithms, "few" of the immediate past observations were used to determine the cut-off ash value. These "few" observations were called the window width . The window width was kept constant in some variants of this class of algorithms. The other variants of this class were an improvement over the fixed window width algorithms. Here, the window widths were varied rather than kept constant. In these cases, SPC was used to determine the window width at any instant. Statistics of the empirical distribution and the normal distribution were used in computation of the cut-off ash value in all the variants of this class of algorithms. The good performance of the developed algorithms

  6. Hybridization, transgressive segregation and evolution of new genetic systems in Drosophila

    Indian Academy of Sciences (India)

    H. A. Ranganath; S. Aruna

    2003-12-01

    Introgressive hybridization facilitates incorporation of genes from one species into the gene pool of another. Studies on long-term effects of introgressive hybridization in animal systems are sparse. Drosophila nasuta ($2n = 8$) and D. albomicans ($2n = 6$)—a pair of allopatric, morphologically almost identical, cross-fertile members of the nasuta subgroup of the immigrans species group—constitute an excellent system to analyse the impact of hybridization followed by transgressive segregation of parental characters in the hybrid progeny. Hybrid populations of D. nasuta and D. albomicans maintained for over 500 generations in the laboratory constitute new recombinant hybrid genomes, here termed cytoraces. The impact of hybridization, followed by introgression and transgressive segregation, on chromosomal constitution and karyotypes, some fitness parameters, isozymes, components of mating behaviour and mating preference reveals a complex pattern of interracial divergence among parental species and cytoraces. This assemblage of characters in different combinations in a laboratory hybrid zone allows us to study the emergence of new genetic systems. Here, we summarize results from our ongoing studies comparing these hybrid cytoraces with the parental species, and discuss the implications of these findings for our understanding of the evolution of new genetic systems.

  7. Segregation distortion of the CTG repeats at the myotonic dystrophy locus

    Energy Technology Data Exchange (ETDEWEB)

    Chakraborty, R.; Stivers, D.N. [Univ. of Texas Houston Health Science Center, Houston, TX (United States); Deka, R.; Yu, Ling M.; Shriver, M.D.; Ferrell, R.E. [Univ. of Pittsburgh Graduate School of Public Health, Pittsburgh, PA (United States)

    1996-07-01

    Myotonic dystrophy (DM), an autosomal dominant neuromuscular disease, is caused by a CTG-repeat expansion, with affected individuals having {ge}50 repeats of this trinucleotide, at the DMPK locus of human chromosome 19q13.3. Severely affected individuals die early in life; the milder form of this disease reduces reproductive ability. Alleles in the normal range of CTG repeats are not as unstable as the (CTG){sub {ge}50} alleles. In the DM families, anticipation and parental bias of allelic expansions have been noted. However, data on mechanism of maintenance of DM in populations are conflicting. We present a maximum-likelihood model for examining segregation distortion of CTG-repeat alleles in normal families. Analyzing 726 meiotic events in 95 nuclear families from the CEPH panel pedigrees, we find evidence of preferential transmission of larger alleles (of size {le}29 repeats) from females (the probability of transmission of larger alleles is .565 {plus_minus} 0.03, different from .5 at P {approx} .028). There is no evidence of segregation distortion during male meiosis. We propose a hypothesis that preferential transmission of larger CTG-repeat alleles during female meiosis can compensate for mutational contraction of repeats within the normal allelic size range, and reduced viability and fertility of affected individuals. Thus, the pool of premutant alleles at the DM locus can be maintained in populations, which can subsequently mutate to the full mutation status to give rise to DM. 31 refs., 1 fig., 5 tabs.

  8. Novel actin filaments from Bacillus thuringiensis form nanotubules for plasmid DNA segregation.

    Science.gov (United States)

    Jiang, Shimin; Narita, Akihiro; Popp, David; Ghoshdastider, Umesh; Lee, Lin Jie; Srinivasan, Ramanujam; Balasubramanian, Mohan K; Oda, Toshiro; Koh, Fujiet; Larsson, Mårten; Robinson, Robert C

    2016-03-01

    Here we report the discovery of a bacterial DNA-segregating actin-like protein (BtParM) from Bacillus thuringiensis, which forms novel antiparallel, two-stranded, supercoiled, nonpolar helical filaments, as determined by electron microscopy. The BtParM filament features of supercoiling and forming antiparallel double-strands are unique within the actin fold superfamily, and entirely different to the straight, double-stranded, polar helical filaments of all other known ParMs and of eukaryotic F-actin. The BtParM polymers show dynamic assembly and subsequent disassembly in the presence of ATP. BtParR, the DNA-BtParM linking protein, stimulated ATP hydrolysis/phosphate release by BtParM and paired two supercoiled BtParM filaments to form a cylinder, comprised of four strands with inner and outer diameters of 57 Å and 145 Å, respectively. Thus, in this prokaryote, the actin fold has evolved to produce a filament system with comparable features to the eukaryotic chromosome-segregating microtubule.

  9. Using Fluorescence Recovery After Photobleaching (FRAP) to study dynamics of the Structural Maintenance of Chromosome (SMC) complex in vivo

    CERN Document Server

    Badrinarayanan, Anjana

    2016-01-01

    The SMC complex, MukBEF, is important for chromosome organization and segregation in Escherichia coli. Fluorescently tagged MukBEF forms distinct spots (or 'foci') in the cell, where it is thought to carry out most of its chromosome associated activities. This chapter outlines the technique of Fluorescence Recovery After Photobleaching (FRAP) as a method to study the properties of YFP-tagged MukB in fluorescent foci. This method can provide important insight into the dynamics of MukB on DNA and be used to study its biochemical properties in vivo.

  10. Educational Justice and Socio-Economic Segregation in Schools

    Science.gov (United States)

    Brighouse, Harry

    2007-01-01

    Sociologists exploring educational injustice often focus on socio-economic segregation as a central measure of injustice. The comprehensive ideal, furthermore, has the idea of socio-economic integration built into it. The current paper argues that socio-economic segregation is valuable only insofar as it serves other, more fundamental values. This…

  11. Coleman Revisited: School Segregation, Peers, and Frog Ponds

    Science.gov (United States)

    Goldsmith, Pat Rubio

    2011-01-01

    Students from minority segregated schools tend to achieve and attain less than similar students from White segregated schools. This study examines whether peer effects can explain this relationship using normative models and frog-pond models. Normative models (where peers become alike) suggest that minority schoolmates are a liability. Frog-pond…

  12. Using the minimum spanning tree to trace mass segregation

    CERN Document Server

    Allison, Richard J; Parker, Richard J; Zwart, Simon F Portegies; de Grijs, Richard; Kouwenhoven, M B N

    2009-01-01

    We present a new method to detect and quantify mass segregation in star clusters. It compares the minimum spanning tree (MST) of massive stars with that of random stars. If mass segregation is present, the MST length of the most massive stars will be shorter than that of random stars. This difference can be quantified (with an associated significance) to measure the degree of mass segregation. We test the method on simulated clusters in both 2D and 3D and show that the method works as expected. We apply the method to the Orion Nebula Cluster (ONC) and show that the method is able to detect the mass segregation in the Trapezium with a `mass segregation ratio' \\Lambda_{MSR}=8.0 \\pm 3.5 (where \\Lambda_{MSR}=1 is no mass segregation) down to 16 \\Msun, and also that the ONC is mass segregated at a lower level (~2.0 \\pm 0.5) down to 5 \\Msun. Below 5 \\Msun we find no evidence for any further mass segregation in the ONC.

  13. 46 CFR 111.60-9 - Segregation of vital circuits.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Segregation of vital circuits. 111.60-9 Section 111.60-9 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING ELECTRIC SYSTEMS-GENERAL REQUIREMENTS Wiring Materials and Methods § 111.60-9 Segregation of vital circuits. (a) General....

  14. 7 CFR 58.332 - Segregation of raw material.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Segregation of raw material. 58.332 Section 58.332 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Procedures § 58.332 Segregation of raw material. The milk and cream received at the dairy plant shall...

  15. Deconstructing Systems of Segregation: Leadership Challenges in an Urban School

    Science.gov (United States)

    DeMatthews, David

    2014-01-01

    Special education policies can create structures of segregation and inequality. School leaders are often tasked with dismantling these structures while meeting expectations related to accountability policies. This case study involves a new principal at an urban school in a district with a long history of segregation reassigned to work at one of…

  16. 7 CFR 3015.10 - Physical segregation and eligibility.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 15 2010-01-01 2010-01-01 false Physical segregation and eligibility. 3015.10 Section 3015.10 Agriculture Regulations of the Department of Agriculture (Continued) OFFICE OF THE CHIEF....10 Physical segregation and eligibility. Except as provided in § 3015.11, awarding agencies shall...

  17. 27 CFR 24.191 - Segregation of operations.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Segregation of operations. 24.191 Section 24.191 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS WINE Production of Effervescent Wine § 24.191 Segregation of...

  18. Pre-Hire Factors and Workplace Ethnic Segregation (discussion paper)

    NARCIS (Netherlands)

    Stromgren, M.; Tammaru, T.; Van Ham, M.; Marcinzak, S.; Stjernstrom, O.; Lindgren, U.

    2011-01-01

    In addition to neighbourhoods of residence, family and places of work play important roles in producing and reproducing ethnic segregation. Therefore, recent research on ethnic segregation and contact is increasingly turning its attention from residential areas towards other important domains of dai

  19. Residential Segregation in United States Cities: A Causal Analysis

    Science.gov (United States)

    Marshall, Harvey; Jiobu, Robert

    1975-01-01

    Using the technique of path analysis and cities as units of analysis, this study investigates the causes of black residential segregation. The data suggest that the relative socioeconomic status of blacks and black population size are important determinants of segregation. Also relevant are percent black and the relative growth rates of the white…

  20. Black Residential Segregation since the 1948 "Shelley v. Kraemer" Decision.

    Science.gov (United States)

    Darden, Joe T.

    1995-01-01

    Assesses the state of black residential segregation since the court case "Shelley v. Kraemer." Focus is placed on metropolitan areas generally and on St. Louis and Detroit, in particular. It is concluded that blacks have made little progress in reducing segregation in housing since the 1948 court case that outlawed restrictive covenants on the…

  1. Measuring Residential Segregation: An Application of Trend Surface Analysis.

    Science.gov (United States)

    Spriggs, William

    1984-01-01

    Presents a measure of racial residential segregation which conforms to the traditional attributes of segregation indices, but includes sensitivity to the spatial patterns of White and non-White residence in a city. Reviews earlier measures, describes the new one, and applies it to racial housing patterns in Norfolk, Virginia, in 1890. (KH)

  2. Patterns of Interethnic Residential Segregation in the Urban Southwest.

    Science.gov (United States)

    Lopez, Manual Mariano

    1981-01-01

    Compares patterns of residential segregation among Mexican Americans, Blacks, and Anglos for 1960 and 1970 and finds that, in spite of a striking similarity in the overall pattern, there have been some important changes. Further, city characteristics found to be good predictors of segregation for 1960 fail to adequately account for the same types…

  3. Effects of Network Segregation in Intergroup Conflict : An Experimental Analysis

    NARCIS (Netherlands)

    Takács, Károly

    2006-01-01

    Dense in-group and scarce out-group relations (network segregation) often support the emergence of conflicts between groups. A key underlying mechanism is social control that helps to overcome the collective action problem within groups, but contributes to harmful conflicts among them in segregated

  4. On the Origin of Mass Segregation in NGC 3603

    Science.gov (United States)

    Pang, Xiaoying; Grebel, Eva K.; Allison, Richard J.; Goodwin, Simon P.; Altmann, Martin; Harbeck, Daniel; Moffat, Anthony F. J.; Drissen, Laurent

    2013-02-01

    We present deep Hubble Space Telescope/Wide Field and Planetary Camera 2 photometry of the young HD 97950 star cluster in the giant H II region NGC 3603. The data were obtained in 1997 and 2007 permitting us to derive membership based on proper motions of the stars. Our data are consistent with an age of 1 Myr for the HD 97950 cluster. A possible age spread, if present in the cluster, appears to be small. The global slope of the incompleteness-corrected mass function for member stars within 60'' is Γ = -0.88 ± 0.15, which is flatter than the value of a Salpeter slope of -1.35. The radially varying mass function shows pronounced mass segregation ranging from slopes of -0.26 ± 0.32 in the inner 5'' to -0.94 ± 0.36 in the outermost annulus (40''-60''). Stars more massive than 50 M ⊙ are found only in the cluster center. The Λ minimum spanning tree technique confirms significant mass segregation down to 30 M ⊙. The dependence of Λ on mass, i.e., that high-mass stars are more segregated than low-mass stars, and the (weak) dependence of the velocity dispersion on stellar mass might imply that the mass segregation is dynamical in origin. While primordial segregation cannot be excluded, the properties of the mass segregation indicate that dynamical mass segregation may have been the dominant process for segregation of high-mass stars.

  5. "Brown" at 62: School Segregation by Race, Poverty and State

    Science.gov (United States)

    Orfield, Gary; Ee, Jongyeon; Frankenberg, Erica; Siegel-Hawley, Genevieve

    2016-01-01

    As the anniversary of "Brown v. Board of Education" decision arrives again without any major initiatives to mitigate spreading and deepening segregation in the nation's schools, the Civil Rights Project adds to a growing national discussion with a research brief drawn from a much broader study of school segregation to be published in…

  6. A Contribution to the Debate on Homogamy, Propinquity, and Segregation.

    Science.gov (United States)

    Morgan, Barrie S.

    1981-01-01

    Investigated the impact of the residential segregation of social status groups on choice of marriage partner in New Zealand. Data suggested that homogamy and propinquity are independent influences on choice of a spouse. Segregation does not interact with distance to circumscribe choice, but it is important in its own right. (Author)

  7. Forced axial segregation in axially inhomogeneous rotating systems

    NARCIS (Netherlands)

    Gonzalez, S.; Windows-Yule, C.R.; Luding, S.; Parker, D.J.; Thornton, A.R.

    2015-01-01

    Controlling segregation is both a practical and a theoretical challenge. Using a novel drum design comprising concave and convex geometry, we explore, through the application of both discrete particle simulations and positron emission particle tracking, a means by which radial size segregation may b

  8. Gametocidal chromosomes enhancing chromosome aberration in common wheat induced by 5-azacytidine.

    Science.gov (United States)

    Su, W-Y; Cong, W-W; Shu, Y-J; Wang, D; Xu, G-H; Guo, C-H

    2013-01-01

    The gametocidal (Gc) chromosome from Aegilops spp induces chromosome mutation, which is introduced into common wheat as a tool of chromosome manipulation for genetic improvement. The Gc chromosome functions similar to a restriction-modification system in bacteria, in which DNA methylation is an important regulator. We treated root tips of wheat carrying Gc chromosomes with the hypomethylation agent 5-azacytidine; chromosome breakage and micronuclei were observed in these root tips. The frequency of aberrations differed in wheat containing different Gc chromosomes, suggesting different functions inducing chromosome breakage. Gc chromosome 3C caused the greatest degree of chromosome aberration, while Gc chromosome 3C(SAT) and 2C caused only slight chromosome aberration. Gc chromosome 3C induced different degrees of chromosome aberration in wheat varieties Triticum aestivum var. Chinese Spring and Norin 26, demonstrating an inhibition function in common wheat. PMID:23884766

  9. Segregation and differential settling in flocculated tailings

    Energy Technology Data Exchange (ETDEWEB)

    Farinato, R.S.; Mahmoudkhani, A.; Fenderson, T.; Watson, P. [Kemira, Atlanta, GA (United States)

    2010-07-01

    Untreated oil sands tailings have a high solids content, have poor dewaterability, and contain no aggregates. This PowerPoint presentation investigated segregation and differential settling in flocculated tailings. Tailings were treated with gypsum and various polymers. Cylinder settling, dynamic rheometry, particle size analysis, and microscopy techniques were used to characterize the composite tailings. The particles sizes of the samples were evaluated in relation to shear rate, bed depth, and treatment. The study showed that the gypsum-treated tailings had small aggregates, size stratification, a high solids content, and poor dewaterability. The polymer N-treated tailings had the lowest solids content, good dewaterability, and weak aggregates. The polymer A-treated tailings had a low solids content, very good dewaterability, and strong aggregates. The addition of a coagulant to the polymer-A treated tailings provided weaker aggregates and a higher solids content. tabs., figs.

  10. Ethnic Segregation in Arizona Charter Schools

    Directory of Open Access Journals (Sweden)

    Casey D. Cobb

    1999-01-01

    Full Text Available Among the criticisms of charter schools is their potential to further stratify schools along ethnic and class lines. This study addressed whether Arizona charter schools are more ethnically segregated than traditional public schools. In 1996-97, Arizona had nearly one in four of all charter schools in the United States. The analysis involved a series of comparisons between the ethnic compositions of adjacent charter and public schools in Arizona's most populated region and its rural towns. This methodology differed from the approach of many evaluations of charter schools and ethnic stratification in that it incorporated the use of geographic maps to compare schools' ethnic make-ups. The ethnic compositions of 55 urban and 57 rural charter schools were inspected relative to their traditional public school neighbors.

  11. Heider balance, asymmetric ties, and gender segregation

    CERN Document Server

    Krawczyk, Małgorzata J; Hernández-Ramirez, Eric; Naumis, Gerardo G; Kułakowski, Krzysztof

    2015-01-01

    To remove a cognitive dissonance in interpersonal relations, people tend to divide our acquaintances into friendly and hostile parts, both groups internally friendly and mutually hostile. This process is modeled as an evolution towards the Heider balance. A set of differential equations have been proposed and validated (Kulakowski {\\it et al}, IJMPC 16 (2005) 707) to model the Heider dynamics of this social and psychological process. Here we generalize the model by including the initial asymmetry of the interprersonal relations and the direct reciprocity effect which removes this asymmetry. Our model is applied to the data on enmity and friendship in 37 school classes and 4 groups of teachers in M\\'exico. For each class, a stable balanced partition is obtained into two groups. The gender structure of the groups reveals stronger gender segregation in younger classes, i.e. of age below 12 years, a fact consistent with other general empirical results.

  12. Lesbian community: from sisterhood to segregation.

    Science.gov (United States)

    Jo, Bev

    2005-01-01

    This article is about the Lesbian-hatred the author and her first lover experienced as teenagers and how finding a strong Lesbian-identified community in 1970 made all the difference for her as a life-long Lesbian. The Lesbian Feminist politics and ideals of equality and support and questioning all patriarchal/heterosexual/mainstream values and oppressive attitudes in the Lesbian community also made a huge difference for her since she is working-class. It was a wonderful time of female-only space with many kinds of events, and later Lesbian writing and Lesbian music (euphemistically called "Women's Music.") That community is mostly gone now and what remains is often segregated by more privileged Lesbians from less privileged Lesbians because of classism and other oppressions. Increasing acceptance of "Male to Female Transsexuals" as Lesbians, as well as increased embracing of male-identified "femininity," continues to damage what remains of Lesbian community. PMID:19780271

  13. Heider balance, asymmetric ties, and gender segregation

    Science.gov (United States)

    Krawczyk, Małgorzata J.; del Castillo-Mussot, Marcelo; Hernández-Ramírez, Eric; Naumis, Gerardo G.; Kułakowski, Krzysztof

    2015-12-01

    To remove a cognitive dissonance in interpersonal relations, people tend to divide their acquaintances into friendly and hostile parts, both groups internally friendly and mutually hostile. This process is modeled as an evolution toward the Heider balance. A set of differential equations have been proposed and validated (Kułakowski et al., 2005) to model the Heider dynamics of this social and psychological process. Here we generalize the model by including the initial asymmetry of the interpersonal relations and the direct reciprocity effect which removes this asymmetry. Our model is applied to the data on enmity and friendship in 37 school classes and 4 groups of teachers in México. For each class, a stable balanced partition is obtained into two groups. The gender structure of the groups reveals stronger gender segregation in younger classes, i.e. of age below 12 years, a fact consistent with other general empirical results.

  14. Stable Chromosome Condensation Revealed by Chromosome Conformation Capture.

    Science.gov (United States)

    Eagen, Kyle P; Hartl, Tom A; Kornberg, Roger D

    2015-11-01

    Chemical cross-linking and DNA sequencing have revealed regions of intra-chromosomal interaction, referred to as topologically associating domains (TADs), interspersed with regions of little or no interaction, in interphase nuclei. We find that TADs and the regions between them correspond with the bands and interbands of polytene chromosomes of Drosophila. We further establish the conservation of TADs between polytene and diploid cells of Drosophila. From direct measurements on light micrographs of polytene chromosomes, we then deduce the states of chromatin folding in the diploid cell nucleus. Two states of folding, fully extended fibers containing regulatory regions and promoters, and fibers condensed up to 10-fold containing coding regions of active genes, constitute the euchromatin of the nuclear interior. Chromatin fibers condensed up to 30-fold, containing coding regions of inactive genes, represent the heterochromatin of the nuclear periphery. A convergence of molecular analysis with direct observation thus reveals the architecture of interphase chromosomes. PMID:26544940

  15. Protein diversity confers specificity in plasmid segregation.

    Science.gov (United States)

    Fothergill, Timothy J G; Barillà, Daniela; Hayes, Finbarr

    2005-04-01

    The ParG segregation protein (8.6 kDa) of multidrug resistance plasmid TP228 is a homodimeric DNA-binding factor. The ParG dimer consists of intertwined C-terminal domains that adopt a ribbon-helix-helix architecture and a pair of flexible, unstructured N-terminal tails. A variety of plasmids possess partition loci with similar organizations to that of TP228, but instead of ParG homologs, these plasmids specify a diversity of unrelated, but similarly sized, partition proteins. These include the proteobacterial pTAR, pVT745, and pB171 plasmids. The ParG analogs of these plasmids were characterized in parallel with the ParG homolog encoded by the pseudomonal plasmid pVS1. Like ParG, the four proteins are dimeric. No heterodimerization was detectable in vivo among the proteins nor with the prototypical ParG protein, suggesting that monomer-monomer interactions are specific among the five proteins. Nevertheless, as with ParG, the ParG analogs all possess significant amounts of unordered amino acid residues, potentially highlighting a common structural link among the proteins. Furthermore, the ParG analogs bind specifically to the DNA regions located upstream of their homologous parF-like genes. These nucleoprotein interactions are largely restricted to cognate protein-DNA pairs. The results reveal that the partition complexes of these and related plasmids have recruited disparate DNA-binding factors that provide a layer of specificity to the macromolecular interactions that mediate plasmid segregation. PMID:15805511

  16. Numerous transitions of sex chromosomes in Diptera.

    Directory of Open Access Journals (Sweden)

    Beatriz Vicoso

    2015-04-01

    Full Text Available Many species groups, including mammals and many insects, determine sex using heteromorphic sex chromosomes. Diptera flies, which include the model Drosophila melanogaster, generally have XY sex chromosomes and a conserved karyotype consisting of six chromosomal arms (five large rods and a small dot, but superficially similar karyotypes may conceal the true extent of sex chromosome variation. Here, we use whole-genome analysis in 37 fly species belonging to 22 different families of Diptera and uncover tremendous hidden diversity in sex chromosome karyotypes among flies. We identify over a dozen different sex chromosome configurations, and the small dot chromosome is repeatedly used as the sex chromosome, which presumably reflects the ancestral karyotype of higher Diptera. However, we identify species with undifferentiated sex chromosomes, others in which a different chromosome replaced the dot as a sex chromosome or in which up to three chromosomal elements became incorporated into the sex chromosomes, and others yet with female heterogamety (ZW sex chromosomes. Transcriptome analysis shows that dosage compensation has evolved multiple times in flies, consistently through up-regulation of the single X in males. However, X chromosomes generally show a deficiency of genes with male-biased expression, possibly reflecting sex-specific selective pressures. These species thus provide a rich resource to study sex chromosome biology in a comparative manner and show that similar selective forces have shaped the unique evolution of sex chromosomes in diverse fly taxa.

  17. Experimental determination of the segregation process using computer tomography

    Directory of Open Access Journals (Sweden)

    Konstantin Beckmann

    2016-08-01

    Full Text Available Modelling methods such as DEM and CFD are increasingly used for developing high efficient combine cleaning systems. For this purpose it is necessary to verify the complex segregation and separation processes in the combine cleaning system. One way is to determine the segregation and separation function using 3D computer tomography (CT. This method makes it possible to visualize and analyse the movement behaviour of the components of the mixture during the segregation and separation process as well as the derivation of descriptive process parameters. A mechanically excited miniature test rig was designed and built at the company CLAAS Selbstfahrende Erntemaschinen GmbH to achieve this aim. The investigations were carried out at the Fraunhofer Institute for Integrated Circuits IIS. Through the evaluation of the recorded images the segregation process is described visually. A more detailed analysis enabled the development of segregation and separation function based on the different densities of grain and material other than grain.

  18. Experimental determination of the segregation process using computer tomography

    Directory of Open Access Journals (Sweden)

    Konstantin Beckmann

    2016-07-01

    Full Text Available Modelling methods such as DEM and CFD are increasingly used for developing high efficient combine cleaning systems. For this purpose it is necessary to verify the complex segregation and separation processes in the combine cleaning system. One way is to determine the segregation and separation function using 3D computer tomography (CT. This method makes it possible to visualize and analyse the movement behaviour of the components of the mixture during the segregation and separation process as well as the derivation of descriptive process parameters. A mechanically excited miniature test rig was designed and built at the company CLAAS Selbstfahrende Erntemaschinen GmbH to achieve this aim. The investigations were carried out at the Fraunhofer Institute for Integrated Circuits IIS. Through the evaluation of the recorded images the segregation process is described visually. A more detailed analysis enabled the development of segregation and separation function based on the different densities of grain and material other than grain.

  19. Mass Segregation of Embedded Clusters in the Milky Way

    CERN Document Server

    Er, Xinyue; Fu, Yanning

    2012-01-01

    Embedded clusters are ideal laboratories to understand the early phase of the dynamical evolution of clusters as well as the massive star formation. An interesting observational phenomenon is that some of the embedded clusters show mass segregation, i.e., the most massive stars are preferentially found near the cluster center. In this paper, we develop a new approach to describe mass segregation. Using this approach and the Two Micron All Sky Survey Point Source Catalog (2MASS PSC), we analyze eighteen embedded clusters in the Galaxy. We find that eleven of them are mass-segregated and that the others are non-mass-segregated. No inversely mass-segregated cluster is found.

  20. Uncovering Mass Segregation with Galaxy Analogues in Dark Matter Simulations

    CERN Document Server

    Joshi, Gandhali D; Wadsley, James

    2016-01-01

    We investigate mass segregation in group and cluster environments by identifying galaxy analogues in high-resolution dark matter simulations. Subhalos identified by the AHF and ROCKSTAR halo finders have similar mass functions, independent of resolution, but different radial distributions due to significantly different subhalo hierarchies. We propose a simple way to classify subhalos as galaxy analogues. The radial distributions of galaxy analogues agree well at large halo-centric radii for both AHF and ROCKSTAR but disagree near parent halo centres where the phase-space information used by ROCKSTAR is essential. We see clear mass segregation at small radii (within $0.5\\,r_{vir}$) with average galaxy analogue mass decreasing with radius. Beyond the virial radius, we find a mild trend where the average galaxy analogue mass increases with radius. These mass segregation trends are strongest in small groups and dominated by the segregation of low mass analogues. The lack of mass segregation in massive galaxy anal...

  1. Rapid dynamical mass segregation and properties of fractal star clusters

    CERN Document Server

    Yu, Jincheng; Chen, Li

    2011-01-01

    We investigate the evolution of young star clusters using N-body simulations. We confirm that subvirial and fractal-structured clusters will dynamically mass segregate on a short timescale (within 0.5 Myr). We adopt a modified minimum-spanning-tree (MST) method to measure the degree of mass segregation, demonstrating that the stars escaping from a cluster's potential are important for the temporal dependence of mass segregation in the cluster. The form of the initial velocity distribution will also affect the degree of mass segregation. If it depends on radius, the outer parts of the cluster would expand without undergoing collapse. In velocity space, we find 'inverse mass segregation,' which indicates that massive stars have higher velocity dispersions than their lower-mass counterparts.

  2. The role of temporal coherence in auditory stream segregation

    DEFF Research Database (Denmark)

    Christiansen, Simon Krogholt

    The ability to perceptually segregate concurrent sound sources and focus one’s attention on a single source at a time is essential for the ability to use acoustic information. While perceptual experiments have determined a range of acoustic cues that help facilitate auditory stream segregation...... of auditory processing, the role of auditory preprocessing and temporal coherence in auditory stream formation was evaluated. The computational model presented in this study assumes that auditory stream segregation occurs when sounds stimulate non-overlapping neural populations in a temporally incoherent...... on the stream segregation process was analysed. The model analysis showed that auditory frequency selectivity and physiological forward masking play a significant role in stream segregation based on frequency separation and tone rate. Secondly, the model analysis suggested that neural adaptation...

  3. Mass segregation of embedded clusters in the Milky Way

    Institute of Scientific and Technical Information of China (English)

    Xin-Yue Er; Zhi-Bo Jiang; Yan-Ning Fu

    2013-01-01

    Embedded clusters are ideal laboratories for understanding the early phase of the dynamical evolution of clusters as well as massive star formation.An interesting observational phenomenon is that some of the embedded clusters show mass segregation,i.e.,the most massive stars are preferentially found near the cluster center.We develop a new approach to describe mass segregation.Using this approach and the Two Micron All Sky Survey Point Source Catalog (2MASS PSC),we analyze 18 embedded clusters in the Galaxy.We find that 11 of them are mass-segregated and that the others are not mass-segregated.No inversely mass-segregated cluster is found.

  4. Atomically ordered solute segregation behaviour in an oxide grain boundary

    Science.gov (United States)

    Feng, Bin; Yokoi, Tatsuya; Kumamoto, Akihito; Yoshiya, Masato; Ikuhara, Yuichi; Shibata, Naoya

    2016-01-01

    Grain boundary segregation is a critical issue in materials science because it determines the properties of individual grain boundaries and thus governs the macroscopic properties of materials. Recent progress in electron microscopy has greatly improved our understanding of grain boundary segregation phenomena down to atomistic dimensions, but solute segregation is still extremely challenging to experimentally identify at the atomic scale. Here, we report direct observations of atomic-scale yttrium solute segregation behaviours in an yttria-stabilized-zirconia grain boundary using atomic-resolution energy-dispersive X-ray spectroscopy analysis. We found that yttrium solute atoms preferentially segregate to specific atomic sites at the core of the grain boundary, forming a unique chemically-ordered structure across the grain boundary. PMID:27004614

  5. Development and chromosome mechanics in nematodes: Results from IML-1

    Science.gov (United States)

    Nelson, G. A.; Schubert, W. W.; Kazarians, G. A.; Richards, G. F.

    1994-01-01

    A subset of the Caenorhabditis elegans nematodes flown aboard Biorack on IML-1 was analyzed for the fidelity of development and the mechanics of chromosomes at meiosis. To assess meiosis, mutant worms marked at two linked or unlinked loci were inoculated as heterozygous hermaphrodites and allowed to self fertilize. Mendelian segregation ratios and recombination frequency were measured for offspring produced at 1XG or in microgravity. To assess development, worms and embryos were fixed and stained with the DNA dye, Diamidinophenolindole (DAPI), or antibodies specific for antigens expressed in germ cells, pharyngeal and body wall muscles, and gut cells. The distribution of cytoplasmic determinants, cell nuclei counts and positions were scored to assess symmetry relations and anatomical features.

  6. Familial transmission of a deletion of chromosome 21 derived from a translocation between chromosome 21 and an inverted chromosome 22.

    Science.gov (United States)

    Aviv, H; Lieber, C; Yenamandra, A; Desposito, F

    1997-06-27

    Chromosome analysis of a newborn boy with Down syndrome resulted in the identification of a family with an unusual derivative chromosome 22. The child has 46 chromosomes, including two chromosomes 21, one normal chromosome 22, and a derivative chromosome 22. Giemsa banding and fluorescent in situ hybridization (FISH) studies show that the derivative chromosome is chromosome 22 with evidence of both paracentric and pericentric inversions, joined to the long arm of chromosome 21 from 21q21.2 to qter. The rearrangement results in partial trisomy 21 extending from 21q21.2 to 21q terminus in the patient. The child's mother, brother, maternal aunt, and maternal grandmother are all carriers of the derivative chromosome. All have 45 chromosomes, with one normal chromosome 21, one normal chromosome 22, and the derivative chromosome 22. The rearrangement results in the absence of the short arm, the centromere, and the proximal long arm of chromosome 21 (del 21pter-21q21.2) in carriers. Carriers of the derivative chromosome in this family have normal physical appearance, mild learning disabilities and poor social adjustment. PMID:9182781

  7. Meiosis and chromosome painting of sex chromosome systems in Ceboidea.

    Science.gov (United States)

    Mudry, M D; Rahn, I M; Solari, A J

    2001-06-01

    The identity of the chromosomes involved in the multiple sex system of Alouatta caraya (Aca) and the possible distribution of this system among other Ceboidea were investigated by chromosome painting of mitotic cells from five species and by analysis of meiosis at pachytene in two species. The identity of the autosome #7 (X2) involved in the multiple system of Aca and its breakage points were demonstrated by both meiosis and chromosome painting. These features are identical to those described by Consigliere et al. [1996] in Alouatta seniculus sara (Assa) and Alouatta seniculus arctoidea (Asar). This multiple system was absent in the other four Ceboidea species studied here. However, data from the literature strongly suggest the presence of this multiple in other members of this genus. The presence of this multiple system among several species and subspecies that show high levels of chromosome rearrangements may suggest a special selective value of this multiple. The meiotic features of the sex systems of Aca and Cebus apella paraguayanus (Cap) are strikingly different at pachytene, as the latter system is similar to the sex pair of man and other primates. The relatively large genetic distances between species presently showing this multiple system suggest that its origin is not recent. Other members of the same genus should be investigated at meiosis and by chromosome painting in order to know the extent and distribution of this complex sex-chromosome system. PMID:11376445

  8. Generation of a panel of antibodies against proteins encoded on human chromosome 21

    Directory of Open Access Journals (Sweden)

    Wiseman Frances K

    2010-08-01

    Full Text Available Abstract Background Down syndrome (DS is caused by trisomy of all or part of chromosome 21. To further understanding of DS we are working with a mouse model, the Tc1 mouse, which carries most of human chromosome 21 in addition to the normal mouse chromosome complement. This mouse is a model for human DS and recapitulates many of the features of the human syndrome such as specific heart defects, and cerebellar neuronal loss. The Tc1 mouse is mosaic for the human chromosome such that not all cells in the model carry it. Thus to help our investigations we aimed to develop a method to identify cells that carry human chromosome 21 in the Tc1 mouse. To this end, we have generated a panel of antibodies raised against proteins encoded by genes on human chromosome 21 that are known to be expressed in the adult brain of Tc1 mice Results We attempted to generate human specific antibodies against proteins encoded by human chromosome 21. We selected proteins that are expressed in the adult brain of Tc1 mice and contain regions of moderate/low homology with the mouse ortholog. We produced antibodies to seven human chromosome 21 encoded proteins. Of these, we successfully generated three antibodies that preferentially recognise human compared with mouse SOD1 and RRP1 proteins on western blots. However, these antibodies did not specifically label cells which carry a freely segregating copy of Hsa21 in the brains of our Tc1 mouse model of DS. Conclusions Although we have successfully isolated new antibodies to SOD1 and RRP1 for use on western blots, in our hands these antibodies have not been successfully used for immunohistochemistry studies. These antibodies are freely available to other researchers. Our data high-light the technical difficulty of producing species-specific antibodies for both western blotting and immunohistochemistry.

  9. Mitotic segregation in intergeneric hybrids of yeast to give novel genetic segregants

    International Nuclear Information System (INIS)

    Two strains of yeast, Yarrowia lipolytica and Saccharomycopsis fibuligera, have a filamentous growth form in addition to budding cells. Y. lipolytica produces lipases and is used in the production of citric acid while W. fibuligera produces amylases and is used in the production of rice wine. In the present report, we made a study of the following: (i) karyotypes of the two yeast strains to obtain a better understanding of their genetic relatedness, (ii) genetic crosses between the two strains to produce intergeneric hybrids, and (iii) pattern of genetic segregation of the intergeneric hybrids via the mitotic process. The results of our studies showed that the two yeast strains were genetically related and that putative intergeneric hybrids were obtained by a genetic crossing of the strains. The hybrids were relatively stable in mitosis as compared to their parent strains. However, in prolonged vegetative propagation, the hybrids gave rise to genetic segregants, most of which were of either of the two parent phenotypes. A number of the segregants had phenotypes which combined those of the parental types. Of considerable significance was that yet a few others were novel as they exhibited phenotypes not hitherto seen for both parent strains. (author). 9 refs, 5 tabs

  10. Park7, a novel locus for autosomal recessive early-onset parkinsonism, on chromosome 1p36

    OpenAIRE

    Duijn, Cock; Breedveld, Guido; Horstink, Marten; Sandkuijl, Lodewijk; Oostra, Ben; Swieten, J. C.; Bonifati, Vincenzo; Galjaard, Robert-Jan; Houwing-Duistermaat, Jeanine; Testers, L.; Dekker, Marieke; Snijders, Pieter; Heutink, Peter

    2001-01-01

    textabstractAlthough the role of genetic factors in the origin of Parkinson disease has long been disputed, several genes involved in autosomal dominant and recessive forms of the disease have been localized. Mutations associated with early-onset autosomal recessive parkinsonism have been identified in the Parkin gene, and recently a second gene, PARK6, involved in early-onset recessive parkinsonism was localized on chromosome 1p35-36. We identified a family segregating early-onset parkinsoni...

  11. Chromosome Architecture and Genome Organization

    OpenAIRE

    Giorgio Bernardi

    2015-01-01

    How the same DNA sequences can function in the three-dimensional architecture of interphase nucleus, fold in the very compact structure of metaphase chromosomes and go precisely back to the original interphase architecture in the following cell cycle remains an unresolved question to this day. The strategy used to address this issue was to analyze the correlations between chromosome architecture and the compositional patterns of DNA sequences spanning a size range from a few hundreds to a few...

  12. Chromosome evolution in Neotropical butterflies

    OpenAIRE

    Saura, Anssi; Von Schoultz, Barbara; Saura, Anja O.; Brown, Keith S., Jr.

    2013-01-01

    We list the chromosome numbers for 65 species of Neotropical Hesperiidae and 104 species or subspecies of Pieridae. In Hesperiidae the tribe Pyrrhopygini have a modal n = 28, Eudaminae and Pyrgini a modal n = 31, while Hesperiinae have n = around 29. Among Pieridae, Coliadinae have a strong modal n = 31 and among Pierinae Anthocharidini are almost fixed for n = 15 while Pierini vary with n = 26 as the most common chromosome number. Dismorphiinae show wide variation. We discuss these results i...

  13. Methods for chromosome-specific staining

    Science.gov (United States)

    Gray, Joe W.; Pinkel, Daniel

    1995-01-01

    Methods and compositions for chromosome-specific staining are provided. Compositions comprise heterogenous mixtures of labeled nucleic acid fragments having substantially complementary base sequences to unique sequence regions of the chromosomal DNA for which their associated staining reagent is specific. Methods include methods for making the chromosome-specific staining compositions of the invention, and methods for applying the staining compositions to chromosomes.

  14. Origin and domestication of papaya Yh chromosome

    Science.gov (United States)

    Sex in papaya is controlled by a pair of nascent sex chromosomes. Females are XX, and two slightly different Y chromosomes distinguish males (XY) and hermaphrodites (XYh). The hermaphrodite-specific region of the Yh chromosome (HSY) and its X chromosome counterpart were sequenced and analyzed previo...

  15. Chromosome evolution in Neotropical butterflies.

    Science.gov (United States)

    Saura, Anssi; Von Schoultz, Barbara; Saura, Anja O; Brown, Keith S

    2013-06-01

    We list the chromosome numbers for 65 species of Neotropical Hesperiidae and 104 species or subspecies of Pieridae. In Hesperiidae the tribe Pyrrhopygini have a modal n = 28, Eudaminae and Pyrgini a modal n = 31, while Hesperiinae have n = around 29. Among Pieridae, Coliadinae have a strong modal n = 31 and among Pierinae Anthocharidini are almost fixed for n = 15 while Pierini vary with n = 26 as the most common chromosome number. Dismorphiinae show wide variation. We discuss these results in the context of chromosome numbers of over 1400 Neotropical butterfly species and subspecies derived from about 3000 populations published here and in earlier papers of a series. The overall results show that many Neotropical groups are characterized by karyotype instability with several derived modal numbers or none at all, while almost all taxa of Lepidoptera studied from the other parts of the world have one of n = 29-31 as modal numbers. Possibly chromosome number changes become fixed in the course of speciation driven by biotic interactions. Population subdivision and structuring facilitate karyotype change. Factors that stabilize chromosome numbers include hybridization among species sharing the same number, migration, sexual selection and possibly the distribution of chromosomes within the nucleus. PMID:23865963

  16. Taylor revisited: Gender segregation and division of labour in the ICT - sector (information and communication technology)

    DEFF Research Database (Denmark)

    Nygaard, Else

    2001-01-01

    Information and communication technology, division of labour, gender segregation, working conditions......Information and communication technology, division of labour, gender segregation, working conditions...

  17. Numerically abnormal chromosome constitutions in humans

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1993-12-31

    Chapter 24, discusses numerically abnormal chromosome constitutions in humans. This involves abnormalities of human chromosome number, including polyploidy (when the number of sets of chromosomes increases) and aneuploidy (when the number of individual normal chromosomes changes). Chapter sections discuss the following chromosomal abnormalities: human triploids, imprinting and uniparental disomy, human tetraploids, hydatidiform moles, anomalies caused by chromosomal imbalance, 13 trisomy (D{sub 1} trisomy, Patau syndrome), 21 trisomy (Down syndrome), 18 trisomy syndrome (Edwards syndrome), other autosomal aneuploidy syndromes, and spontaneous abortions. The chapter concludes with remarks on the nonrandom participation of chromosomes in trisomy. 69 refs., 3 figs., 4 tabs.

  18. Element segregation on the surfaces of pure aluminum foils

    International Nuclear Information System (INIS)

    The surface segregation trend of trace elements in pure aluminum foils was investigated by density functional theory. The model of nine-layer Al(1 0 0) slab substituted partially by trace element atoms was proposed for calculating surface segregation energy. The calculating results show that (i) B, Mg, Si, Ga, Ge, Y, In, Sn, Sb, Pb and Bi exhibit negative segregation energy and possibly move to the surface, while Be, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zr exhibit positive segregation energies and migrated into the bulk; (ii) the segregation energy was found to be related with the covalent radius, the relaxed position at the surface of the substituting atom and the surface energy; (iii) the segregation behavior of trace element generates lots of defects and dislocation, which can increase the initial pitting nucleation sites in the surface of aluminum foils; (iv) the impurity atom concentration was tested with Pb-doped surfaces, the calculated negative segregation energies in all coverage increases rapidly with the Pb coverage. These conclusions are helpful for designing of the chemical composition and to advance the tunnel etching of aluminum foils.

  19. Factors shaping workplace segregation between natives and immigrants.

    Science.gov (United States)

    Strömgren, Magnus; Tammaru, Tiit; Danzer, Alexander M; van Ham, Maarten; Marcińczak, Szymon; Stjernström, Olof; Lindgren, Urban

    2014-04-01

    Research on segregation of immigrant groups is increasingly turning its attention from residential areas toward other important places, such as the workplace, where immigrants can meet and interact with members of the native population. This article examines workplace segregation of immigrants. We use longitudinal, georeferenced Swedish population register data, which enables us to observe all immigrants in Sweden for the period 1990-2005 on an annual basis. We compare estimates from ordinary least squares with fixed-effects regressions to quantify the extent of immigrants' self-selection into specific workplaces, neighborhoods, and partnerships, which may bias more naïve ordinary least squares results. In line with previous research, we find lower levels of workplace segregation than residential segregation. The main finding is that low levels of residential segregation reduce workplace segregation, even after we take into account intermarriage with natives as well as unobserved characteristics of immigrants' such as willingness and ability to integrate into the host society. Being intermarried with a native reduces workplace segregation for immigrant men but not for immigrant women. PMID:24399142

  20. Meiotic behavior and chromosome number of Urochloa adspersa (Trin.) R. D. Webster from the Brazilian Chaco.

    Science.gov (United States)

    Felismino, M F; Maior, R L S; Damasceno, G A; Pott, A; Pagliarini, M S

    2015-01-01

    This is the first report of meiotic division in Uro-chloa adspersa (Trin.) collected from the Brazilian Chaco. Meiotic analyses were performed on three specimens of U. adspersa named G10, G15, and G16. Inflorescences were collected and fixed in a mixture of ethanol and acetic acid (3:1, v/v) for 24 h and then stored in 70% alcohol. Diakinesis revealed different chromosome numbers and ploidy levels. All three plants were polyploids: G10 and G15 exhibited 2n = 6x = 54 chromosomes (arranged in 27 bivalents), while G16 exhibited 2n = 4x = 36 chromosomes (18 bivalents). Meiotic behavior was mainly normal in the hexaploid G15 and the tetraploid G16 (5.3 and 6.2% of the cells were abnormal, respective-ly), revealing only a few meiotic abnormalities that are common to polyploids, i.e., those related to irregular chromosome segregation. G10 exhibited other meiotic abnormalities during meiosis II, such as chromosome stickiness, irregular spindle orientation, and irregular cytokinesis, which led to the formation of a few triads, resulting in 16.9% of the cells being abnormal. The origin of these abnormalities is discussed, and we suggest that the genes that control meiotic steps may be present in the Urochloa gene pool. PMID:26214424