Meiotic Chromosome Segregation in Triploid Strains of Saccharomyces cerevisiae

Abstract Meiotic chromosome pairing in isogenic triploid and tetraploid strains of yeast and the consequences of polyploidy on meiotic chromosome segregation are studied. Synaptonemal complex formation at pachytene was found to be different in the triploid and in the tetraploid. In the triploid, triple-synapsis, that is, the connection of three homologues at a given site, is common. It can even extend all the way along the chromosomes. In the tetraploid, homologous chromosomes mostly come in pairs of synapsed bivalents. Multiple synapsis, that is, synapsis of more than two homologues in one and the same region, was virtually absent in the tetraploid. About five quadrivalents per cell occurred due to the switching of pairing partners. From the frequency of pairing partner switches it can be deduced that in most chromosomes synapsis is initiated primarily at one end, occasionally at both ends and rarely at an additional intercalary position. In contrast to a considerably reduced spore viability (approximately 40%) in the triploid, spore viability is only mildly affected in the tetraploid. The good spore viability is presumably due to the low frequency of quadrivalents and to the highly regular 2:2 segregation of the few quadrivalents that do occur. Occasionally, however, quadrivalents appear to be subject to 3:1 nondisjunction that leads to spore death in the second generation.

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Meiotic disjunction of homologs in Saccharomyces cerevisiae is directed by pairing and recombination of the chromosome arms but not by pairing of the centromeres.

Genetics ◽

10.1093/genetics/119.2.273 ◽

1988 ◽

Vol 119 (2) ◽

pp. 273-287

Author(s):

R T Surosky ◽

B K Tye

Keyword(s):

Saccharomyces Cerevisiae ◽

Chromosome Segregation ◽

Meiotic Chromosome ◽

Chromosomal Rearrangements ◽

Normal Chromosome ◽

Telocentric Chromosome ◽

Meiotic Chromosomes ◽

Chromosome Recombination ◽

Left And Right ◽

Chromosome Iii

Abstract We explored the behavior of meiotic chromosomes in Saccharomyces cerevisiae by examining the effects of chromosomal rearrangements on the pattern of disjunction and recombination of chromosome III during meiosis. The segregation of deletion chromosomes lacking part or all (telocentric) of one arm was analyzed in the presence of one or two copies of a normal chromosome III. In strains containing one normal and any one deletion chromosome, the two chromosomes disjoined in most meioses. In strains with one normal chromosome and both a left and right arm telocentric chromosome, the two telocentrics preferentially disjoined from the normal chromosome. Homology on one arm was sufficient to direct chromosome disjunction, and two chromosomes could be directed to disjoin from a third. In strains containing one deletion chromosome and two normal chromosomes, the two normal chromosomes preferentially disjoined, but in 4-7% of the tetrads the normal chromosomes cosegregated, disjoining from the deletion chromosome. Recombination between the two normal chromosomes or between the deletion chromosome and a normal chromosome increased the probability that these chromosomes would disjoin, although cosegregation of recombinants was observed. Finally, we observed that a derivative of chromosome III in which the centromeric region was deleted and CEN5 was integrated at another site on the chromosome disjoined from a normal chromosome III with fidelity. These studies demonstrate that it is not pairing of the centromeres, but pairing and recombination along the arms of the homologs, that directs meiotic chromosome segregation.

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Variation in Crossover Frequencies Perturb Crossover Assurance Without Affecting Meiotic Chromosome Segregation in Saccharomyces cerevisiae

Genetics ◽

10.1534/genetics.114.172320 ◽

2014 ◽

Vol 199 (2) ◽

pp. 399-412 ◽

Cited By ~ 19

Author(s):

Gurukripa N. Krishnaprasad ◽

Mayakonda T. Anand ◽

Gen Lin ◽

Manu M. Tekkedil ◽

Lars M. Steinmetz ◽

...

Keyword(s):

Saccharomyces Cerevisiae ◽

Chromosome Segregation ◽

Meiotic Chromosome

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The Role of Centromere Alignment in Meiosis I Segregation of Homologous Chromosomes in Saccharomyces cerevisiae

Genetics ◽

10.1093/genetics/153.4.1547 ◽

1999 ◽

Vol 153 (4) ◽

pp. 1547-1560

Author(s):

Cesar E Guerra ◽

David B Kaback

Keyword(s):

Saccharomyces Cerevisiae ◽

Chromosome Segregation ◽

Meiotic Chromosome ◽

Meiotic Spindle ◽

Physical Interaction ◽

Crossing Over ◽

Homologous Chromosomes ◽

Chromosome Alignment ◽

Chromosome I

AbstractDuring meiosis, homologous chromosomes pair and then segregate from each other at the first meiotic division. Homologous centromeres appear to be aligned when chromosomes are paired. The role of centromere alignment in meiotic chromosome segregation was investigated in Saccharomyces cerevisiae diploids that contained one intact copy of chromosome I and one copy bisected into two functional centromere-containing fragments. The centromere on one fragment was aligned with the centromere on the intact chromosome while the centromere on the other fragment was either aligned or misaligned. Fragments containing aligned centromeres segregated efficiently from the intact chromosome, while fragments containing misaligned centromeres segregated much less efficiently from the intact chromosome. Less efficient segregation was correlated with crossing over in the region between the misaligned centromeres. Models that suggest that these crossovers impede proper segregation by preventing either a segregation-promoting chromosome alignment on the meiotic spindle or some physical interaction between homologous centromeres are proposed.

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Meiotic Crossing Over Between Nonhomologous Chromosomes Affects Chromosome Segregation in Yeast

Genetics ◽

10.1093/genetics/146.1.69 ◽

1997 ◽

Vol 146 (1) ◽

pp. 69-78

Author(s):

Sue Jinks-Robertson ◽

Shariq Sayeed ◽

Tamara Murphy

Keyword(s):

Saccharomyces Cerevisiae ◽

Gene Conversion ◽

Chromosome Segregation ◽

Meiotic Recombination ◽

Southern Blot Analysis ◽

Meiotic Chromosome ◽

Crossing Over ◽

Yeast Saccharomyces Cerevisiae ◽

Reciprocal Translocations ◽

Ectopic Recombination

Meiotic recombination between artificial repeats positioned on nonhomologous chromosomes occurs efficiently in the yeast Saccharomyces cerevisiae. Both gene conversion and crossover eventS have been observed, with crossovers yielding reciprocal translocations. In the current study, 5.5-kb ura3 repeats positioned on chromosomes V and XV were used to examine the effect of ectopic recombination on meiotic chromosome segregation. Ura+ random spores were selected and gene conversion vs. crossover events were distinguished by Southern blot analysis. Approximately 15% of the crossover events between chromosomes V and XV were associated with missegregation of one of these chromosomes. The missegregation was manifest as hyperploid spores containing either both translocations plus a normal chromosome, or both normal chromosomes plus one of the translocations. In those cases where it could be analyzed, missegregation occurred at the first meiotic division. These data are discussed in terms of a model in which ectopic crossovers compete efficiently with normal allelic crossovers in directing meiotic chromosome segregation.

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Double or nothing: a Drosophila mutation affecting meiotic chromosome segregation in both females and males.

Genetics ◽

10.1093/genetics/136.3.953 ◽

1994 ◽

Vol 136 (3) ◽

pp. 953-964 ◽

Cited By ~ 2

Author(s):

D P Moore ◽

W Y Miyazaki ◽

J E Tomkiel ◽

T L Orr-Weaver

Keyword(s):

Cell Death ◽

Chromosome Segregation ◽

Sister Chromatid ◽

Meiotic Chromosome ◽

Sister Chromatid Cohesion ◽

Aberrant Chromosome ◽

Chromatid Cohesion ◽

Meiotic Nondisjunction ◽

Lethal Allele ◽

Meiosis I

Abstract We describe a Drosophila mutation, Double or nothing (Dub), that causes meiotic nondisjunction in a conditional, dominant manner. Previously isolated mutations in Drosophila specifically affect meiosis either in females or males, with the exception of the mei-S332 and ord genes which are required for proper sister-chromatid cohesion. Dub is unusual in that it causes aberrant chromosome segregation almost exclusively in meiosis I in both sexes. In Dub mutant females both nonexchange and exchange chromosomes undergo nondisjunction, but the effect of Dub on nonexchange chromosomes is more pronounced. Dub reduces recombination levels slightly. Multiple nondisjoined chromosomes frequently cosegregate to the same pole. Dub results in nondisjunction of all chromosomes in meiosis I of males, although the levels are lower than in females. When homozygous, Dub is a conditional lethal allele and exhibits phenotypes consistent with cell death.

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DBF8, an essential gene required for efficient chromosome segregation in Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.14.9.6350-6360.1994 ◽

1994 ◽

Vol 14 (9) ◽

pp. 6350-6360

Author(s):

F Houman ◽

C Holm

Keyword(s):

Saccharomyces Cerevisiae ◽

Chromosome Segregation ◽

Mutational Analysis ◽

Essential Gene ◽

Chromosome Loss ◽

Temperature Sensitive ◽

Restrictive Temperature ◽

Permissive Temperature ◽

Nonsense Mutations ◽

Carboxy Terminal

To investigate chromosome segregation in Saccharomyces cerevisiae, we examined a collection of temperature-sensitive mutants that arrest as large-budded cells at restrictive temperatures (L. H. Johnston and A. P. Thomas, Mol. Gen. Genet. 186:439-444, 1982). We characterized dbf8, a mutation that causes cells to arrest with a 2c DNA content and a short spindle. DBF8 maps to chromosome IX near the centromere, and it encodes a 36-kDa protein that is essential for viability at all temperatures. Mutational analysis reveals that three dbf8 alleles are nonsense mutations affecting the carboxy-terminal third of the encoded protein. Since all of these mutations confer temperature sensitivity, it appears that the carboxyl-terminal third of the protein is essential only at a restrictive temperature. In support of this conclusion, an insertion of URA3 at the same position also confers a temperature-sensitive phenotype. Although they show no evidence of DNA damage, dbf8 mutants exhibit increased rates of chromosome loss and nondisjunction even at a permissive temperature. Taken together, our data suggest that Dbf8p plays an essential role in chromosome segregation.

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In vivo analysis of the Saccharomyces cerevisiae centromere CDEIII sequence: requirements for mitotic chromosome segregation

Molecular and Cellular Biology ◽

10.1128/mcb.11.10.5212-5221.1991 ◽

1991 ◽

Vol 11 (10) ◽

pp. 5212-5221

Author(s):

B Jehn ◽

R Niedenthal ◽

J H Hegemann

Keyword(s):

Saccharomyces Cerevisiae ◽

Chromosome Segregation ◽

Artificial Chromosome ◽

Complete Information ◽

Saturation Mutagenesis ◽

Chromosome Loss ◽

Single Mutation ◽

Yeast Saccharomyces Cerevisiae ◽

Double Base

In the yeast Saccharomyces cerevisiae, the complete information needed in cis to specify a fully functional mitotic and meiotic centromere is contained within 120 bp arranged in the three conserved centromeric (CEN) DNA elements CDEI, -II, and -III. The 25-bp CDEIII is most important for faithful chromosome segregation. We have constructed single- and double-base substitutions in all highly conserved residues and one nonconserved residue of this element and analyzed the mitotic in vivo function of the mutated CEN DNAs, using an artificial chromosome. The effects of the mutations on chromosome segregation vary between wild-type-like activity (chromosome loss rate of 4.8 x 10(-4)) and a complete loss of CEN function. Data obtained by saturation mutagenesis of the palindromic core sequence suggest asymmetric involvement of the palindromic half-sites in mitotic CEN function. The poor CEN activity of certain single mutations could be improved by introducing an additional single mutation. These second-site suppressors can be found at conserved and nonconserved positions in CDEIII. Our suppression data are discussed in the context of natural CDEIII sequence variations found in the CEN sequences of different yeast chromosomes.

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