Independent chromosome segregation and absence of interchromosomal effect at first meiotic division in male Chinese hamsters heterozygous for two reciprocal translocations

1995 ◽  
Vol 71 (4) ◽  
pp. 380-384 ◽  
Author(s):  
S. Sonta ◽  
M. Tsukasaki ◽  
N. Kohmura ◽  
K. Suzumori
Keyword(s):  
Chromosome Segregation ◽  
Meiotic Division ◽  
Reciprocal Translocations ◽  
Interchromosomal Effect ◽  
Chinese Hamsters

scholarly journals X-chromosome segregation, maternal age and aneuploidy in the XO mouse

1983 ◽  
Vol 41 (1) ◽  
pp. 85-95 ◽  
Author(s):  
J. D. Brook
Keyword(s):  
Chromosome Segregation ◽  
X Chromosome ◽  
Meiotic Division ◽  
Maternal Age ◽  
Cytogenetic Studies

SUMMARYCytogenetic studies have ascertained that the segregation of the X-chromosome, during the first meiotic division of the oocyte in XO mice, occurs at random, contrary to the finding of some earlier authors. The ratio of nullo-X to X-bearing oocytes at ovulation does not change with maternal age. The usefulness of the XO mouse as a model for aneuploidy production in women (Lyon & Hawker, 1973) is discussed.

scholarly journals The spindle checkpoint protein Mad2 regulates APC/C activity during prometaphase and metaphase of meiosis I in Saccharomyces cerevisiae

2011 ◽  
Vol 22 (16) ◽  
pp. 2848-2861 ◽  
Author(s):  
Dai Tsuchiya ◽  
Claire Gonzalez ◽  
Soni Lacefield
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Chromosome Segregation ◽  
Meiotic Division ◽  
Spindle Checkpoint ◽  
Yeast Cells ◽  
Meiotic Cell ◽  
Checkpoint Protein ◽  
Sister Chromatids ◽  
Meiosis I

In many eukaryotes, disruption of the spindle checkpoint protein Mad2 results in an increase in meiosis I nondisjunction, suggesting that Mad2 has a conserved role in ensuring faithful chromosome segregation in meiosis. To characterize the meiotic function of Mad2, we analyzed individual budding yeast cells undergoing meiosis. We find that Mad2 sets the duration of meiosis I by regulating the activity of APCCdc20. In the absence of Mad2, most cells undergo both meiotic divisions, but securin, a substrate of the APC/C, is degraded prematurely, and prometaphase I/metaphase I is accelerated. Some mad2Δ cells have a misregulation of meiotic cell cycle events and undergo a single aberrant division in which sister chromatids separate. In these cells, both APCCdc20 and APCAma1 are prematurely active, and meiosis I and meiosis II events occur in a single meiotic division. We show that Mad2 indirectly regulates APCAma1 activity by decreasing APCCdc20 activity. We propose that Mad2 is an important meiotic cell cycle regulator that ensures the timely degradation of APC/C substrates and the proper orchestration of the meiotic divisions.

Analysis of chromosome segregation in reciprocal translocation carriers

2020 ◽  
pp. 16-18
Author(s):  
З.Н. Тонян ◽  
И.Л. Пуппо ◽  
А.Ф. Сайфитдинова ◽  
Ю.А. Логинова ◽  
О. Г. Чиряева ◽  
...  
Keyword(s):  
Genetic Counseling ◽  
Chromosome Segregation ◽  
Birth Defects ◽  
Reciprocal Translocation ◽  
Spontaneous Abortions ◽  
Meiotic Segregation ◽  
Cleavage Stage ◽  
Reciprocal Translocations ◽  
Recurrent Spontaneous Abortions ◽  
Increased Risk

Аутосомные реципрокные транслокации (АРТ) приводят к повышенному риску образования несбалансированных гамет вследствие патологической сегрегации хромосом в мейозе у носителей. В настоящей статье приведены результаты анализа типов сегрегации для 26 АРТ, а также определены теоретически возможные варианты сегрегации хромосом. В 73% случаев у носителей АРТ в более, чем 50% бластомеров наблюдалось совпадение теоретического и детектируемого типов сегрегации. Полученные данные можно использовать для оптимизации персонализированного медико-генетического консультирования семей, где один из супругов является носителем АРТ, и имеющих репродуктивные проблемы, высокий риск неразвивающейся беременности и/или рождения ребенка с хромосомной патологией. Autosomal reciprocal translocations (ART) lead to an increased risk of imbalanced gametes formation due to pathological meiotic segregation. Segregation type was analyzed and theoretical segregation pattern was determined in 26 cleavage stage embryos in this article. A coincidence of theoretical and detectable segregation types was observed in more than 50 % of blastomeres in 73 % of cases. The data obtained may be used for personalized genetic counseling in families with high risks of recurrent spontaneous abortions, infertility or children with birth defects due to ART.

Live observation of fission yeast meiosis in recombination-deficient mutants

2001 ◽  
Vol 114 (15) ◽  
pp. 2843-2853 ◽  
Author(s):  
Monika Molnar ◽  
Jürg Bähler ◽  
Jürg Kohli ◽  
Yasushi Hiraoka
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Meiotic Division ◽  
Chiasma Formation ◽  
Homologous Chromosomes ◽  
Yeast Meiosis ◽  
Mutant Cells ◽  
Random Level ◽  
Meiosis I ◽  
Chromosome Disjunction

Regular segregation of homologous chromosomes during meiotic divisions is essential for the generation of viable progeny. In recombination-proficient organisms, chromosome disjunction at meiosis I generally occurs by chiasma formation between the homologs (chiasmate meiosis). We have studied meiotic stages in living rec8 and rec7 mutant cells of fission yeast, with special attention to prophase and the first meiotic division. Both rec8 and rec7 are early recombination mutants, and in rec7 mutants, chromosome segregation at meiosis I occurs without any recombination (achiasmate meiosis). Both mutants showed distinct irregularities in nuclear prophase movements. Additionally, rec7 showed an extended first division of variable length and with single chromosomes changing back and forth between the cell poles. Two other early recombination deficient mutants (rec14 and rec15) showed very similar phenotypes to rec7 during the first meiotic division, and the fidelity of achiasmate chromosome segregation slightly exceeded the expected random level. We discuss possible regulatory mechanisms of fission yeast to deal with achiasmate chromosome segregation.

Incomplete pole orientation of kinetochores in complex meiotic metaphase I configurations delays metaphase–anaphase transition in Secale

Genome ◽  
2014 ◽  
Vol 57 (4) ◽  
pp. 233-238
Author(s):  
J. Sybenga
Keyword(s):  
Chromosome Segregation ◽  
Secale Cereale ◽  
Anther Development ◽  
Meiotic Metaphase ◽  
Mild Form ◽  
Reciprocal Translocations ◽  
Chromatid Cohesion ◽  
Pole Orientation ◽  
Metaphase I

To prevent unbalanced chromosome segregation, meiotic metaphase I – anaphase I transition is carefully regulated by delaying anaphase until all kinetochores are well oriented (anaphase checkpoint) in mammals and insects. In plants this has not yet been established. In heterozygotes of two reciprocal translocations of Secale cereale, with one chromosome replaced by its two telocentric arms, anaphase delay was correlated with the orientation of the kinetochores of the complex of five chromosomes. The terminal kinetochores of the half chromosomes were readily elongated and pole oriented. Chains of five chromosomes with all five kinetochores orienting on alternate poles where the first to start anaphase. Kinetochores of two adjacent chromosomes when oriented on the same pole were partly shielded and less well pole directed. Anaphase was delayed. Cells with this configuration accumulated during anther development. Kinetochores in metacentric chromosomes lacking chiasmata in one arm (in trivalents and bivalents) were slightly better pole oriented and delayed anaphase less. Release of chromatid cohesion as triggered by kinetochore stretch is apparently delayed by inadequate exposition and pole orientation of the kinetochores. It is a mild form of an anaphase checkpoint, in normal material synchronizing bivalent segregation.

Analysis Using Sperm-FISH of a Putative Interchromosomal Effect in Boars Carrying Reciprocal Translocations

2009 ◽  
Vol 126 (1-2) ◽  
pp. 194-201 ◽  
Author(s):  
A. Bonnet-Garnier ◽  
S. Guardia ◽  
A. Pinton ◽  
A. Ducos ◽  
M. Yerle
Keyword(s):  
Reciprocal Translocations ◽  
Interchromosomal Effect ◽  
Sperm Fish

Making crossovers during meiosis

2005 ◽  
Vol 33 (6) ◽  
pp. 1451-1455 ◽  
Author(s):  
M.C. Whitby
Keyword(s):  
Genetic Variation ◽  
Homologous Recombination ◽  
Chromosome Segregation ◽  
Meiotic Recombination ◽  
Meiotic Division ◽  
Holliday Junctions ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Dna Junctions

Homologous recombination (HR) is required to promote both correct chromosome segregation and genetic variation during meiosis. For this to be successful recombination intermediates must be resolved to generate reciprocal exchanges or ‘crossovers’ between the homologous chromosomes (homologues) during the first meiotic division. Crossover recombination promotes faithful chromosome segregation by establishing connections (chiasmata) between the homologues, which help guide their proper bipolar alignment on the meiotic spindle. Recent studies of meiotic recombination in both the budding and fission yeasts have established that there are at least two pathways for generating crossovers. One pathway involves the resolution of fully ligated four-way DNA junctions [HJs (Holliday junctions)] by an as yet unidentified endonuclease. The second pathway appears to involve the cleavage of the precursors of ligated HJs, namely displacement (D) loops and unligated/nicked HJs, by the Mus81-Eme1/Mms4 endonuclease.

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