Goldway M, Arbel T, Simchen G
Department of Genetics, Hebrew University of Jerusalem, Israel.
Genetics. 1993 Feb;133(2):149-58. doi: 10.1093/genetics/133.2.149.
A yeast strain, in which nondisjunction of chromosome III at the first meiotic division could be assayed, was constructed. Using chromosome fragmentation plasmids, chromosomal fragments (CFs) were derived in isogenic strains from six sites along chromosome III and one site on chromosome VII. Whereas the presence of the CFs derived from chromosome III increased considerably the meiosis I nondisjunction of that chromosome, the CF derived from chromosome VII had no effect on chromosome III segregation. The effects of the chromosome III-derived fragments were not linearly related to fragment length. Two regions, one of 12 kb in size located at the left end of the chromosome, and the other of 5 kb, located at the center of the right arm, were found to have profound effects on chromosome III nondisjunction. Most disomics arising from meioses in strains containing chromosome III CFs did not contain the CF; thus it appears that the two chromosome III homologs had segregated away from the CF. Among the disomics, recombination between the homologous chromosomes III was lower than expected from the genetic distance, while recombination between one of the chromosomes III and the fragment was frequent. We suggest that there are sites along the chromosome that are more involved than others in the pairing of homologous chromosomes and that the pairing between fragment and homologs involves recombination among these latter elements.
构建了一种酵母菌株，可用于检测第一次减数分裂时第三条染色体的不分离情况。利用染色体断裂质粒，在同基因菌株中从第三条染色体上的六个位点以及第七条染色体上的一个位点获得了染色体片段（CFs）。源自第三条染色体的CFs的存在显著增加了该染色体的减数分裂I不分离情况，而源自第七条染色体的CF对第三条染色体的分离没有影响。源自第三条染色体的片段的影响与片段长度并非线性相关。发现了两个区域，一个大小为12 kb，位于染色体左端，另一个为5 kb，位于右臂中心，它们对第三条染色体的不分离有深远影响。在含有第三条染色体CFs的菌株减数分裂产生的大多数二体中并不包含CF；因此，似乎两条第三条染色体同源物已与CF分离。在二体中，同源第三条染色体之间的重组低于根据遗传距离预期的水平，而其中一条第三条染色体与片段之间的重组很频繁。我们认为，沿着染色体存在一些位点，它们在同源染色体配对中比其他位点更重要，并且片段与同源物之间的配对涉及这些后者元件之间的重组。
