Guacci V, Kaback D B
Department of Microbiology and Molecular Genetics, UMDNJ-New Jersey Medical School, Graduate School of Biomedical Sciences, Newark 07103.
Genetics. 1991 Mar;127(3):475-88. doi: 10.1093/genetics/127.3.475.
Distributive disjunction is defined as the first division meiotic segregation of either nonhomologous chromosomes that lack homologs or homologous chromosomes that have not recombined. To determine if chromosomes from the yeast Saccharomyces cerevisiae were capable of distributive disjunction, we constructed a strain that was monosomic for both chromosome I and chromosome III and analyzed the meiotic segregation of the two monosomic chromosomes. In addition, we bisected chromosome I into two functional chromosome fragments, constructed strains that were monosomic for both chromosome fragments and examined meiotic segregation of the chromosome fragments in the monosomic strains. The two nonhomologous chromosomes or chromosome fragments appeared to segregate from each other in approximately 90% of the asci analyzed, indicating that yeast chromosomes were capable of distributive disjunction. We also examined the ability of a small nonhomologous centromere containing plasmid to participate in distributive disjunction with the two nonhomologous monosomic chromosomes. The plasmid appeared to efficiently participate with the two full length chromosomes suggesting that distributive disjunction in yeast is not dependent on chromosome size. Thus, distributive disjunction in S. cerevisiae appears to be different from Drosophila melanogaster where a different sized chromosome is excluded from distributive disjunction when two similar size nonhomologous chromosomes are present.
分布式分离被定义为缺乏同源物的非同源染色体或未发生重组的同源染色体的第一次减数分裂分离。为了确定来自酿酒酵母的染色体是否能够进行分布式分离，我们构建了一个对染色体I和染色体III均为单体的菌株，并分析了这两条单体染色体的减数分裂分离情况。此外，我们将染色体I一分为二，形成两个功能性染色体片段，构建了对这两个染色体片段均为单体的菌株，并检测了单体菌株中染色体片段的减数分裂分离情况。在分析的大约90%的子囊中，这两条非同源染色体或染色体片段似乎彼此分离，表明酵母染色体能够进行分布式分离。我们还检测了一个含有小的非同源着丝粒的质粒与两条非同源单体染色体参与分布式分离的能力。该质粒似乎能有效地与两条全长染色体一起参与分离，这表明酵母中的分布式分离不依赖于染色体大小。因此，酿酒酵母中的分布式分离似乎与黑腹果蝇不同，在黑腹果蝇中，当存在两条大小相似的非同源染色体时，不同大小的染色体被排除在分布式分离之外。
