Krawchuk M D, Wahls W P
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.
Genetics. 1999 Sep;153(1):49-55. doi: 10.1093/genetics/153.1.49.
Recent evidence suggests that the position of reciprocal recombination events (crossovers) is important for the segregation of homologous chromosomes during meiosis I and sister chromatids during meiosis II. We developed genetic mapping functions that permit the simultaneous analysis of centromere-proximal crossover recombination and the type of segregation error leading to aneuploidy. The mapping functions were tested in a study of the rec8, rec10, and rec11 mutants of fission yeast. In each mutant we monitored each of the three chromosome pairs. Between 38 and 100% of the chromosome segregation errors in the rec8 mutants were due to meiosis I nondisjunction of homologous chromosomes. The remaining segregation errors were likely the result of precocious separation of sister chromatids, a previously described defect in the rec8 mutants. Between 47 and 100% of segregation errors in the rec10 and rec11 mutants were due to nondisjunction of sister chromatids during meiosis II. In addition, centromere-proximal recombination was reduced as much as 14-fold or more on chromosomes that had experienced nondisjunction. These results demonstrate the utility of the new mapping functions and support models in which sister chromatid cohesion and crossover position are important determinants for proper chromosome segregation in each meiotic division.
近期证据表明，相互重组事件（交叉互换）的位置对于减数分裂I期间同源染色体的分离以及减数分裂II期间姐妹染色单体的分离至关重要。我们开发了遗传定位函数，可同时分析着丝粒近端交叉互换重组以及导致非整倍体的分离错误类型。这些定位函数在一项关于裂殖酵母rec8、rec10和rec11突变体的研究中进行了测试。在每个突变体中，我们监测了三对染色体中的每一对。rec8突变体中38%至100%的染色体分离错误是由于同源染色体在减数分裂I时不分离所致。其余的分离错误可能是姐妹染色单体过早分离的结果，这是rec8突变体中先前描述过的一种缺陷。rec10和rec11突变体中47%至100%的分离错误是由于减数分裂II期间姐妹染色单体不分离所致。此外，在经历了不分离的染色体上，着丝粒近端重组减少了多达14倍或更多。这些结果证明了新定位函数的实用性，并支持了这样的模型，即姐妹染色单体黏连和交叉互换位置是每个减数分裂过程中染色体正确分离的重要决定因素。
