Meneely Philip M, Farago Anna F, Kauffman Tate M
Department of Biology, Haverford College, Pennsylvania 19041, USA.
Genetics. 2002 Nov;162(3):1169-77. doi: 10.1093/genetics/162.3.1169.
Regulation of both the number and the location of crossovers during meiosis is important for normal chromosome segregation. We used sequence-tagged site polymorphisms to examine the distribution of all crossovers on the X chromosome during oogenesis and on one autosome during both oogenesis and spermatogenesis in Caenorhabditis elegans. The X chromosome has essentially one crossover during oogenesis, with only three possible double crossover exceptions among 220 recombinant X chromosomes. All three had one of the two crossovers in the same chromosomal interval, suggesting that crossovers in that interval do not cause interference. No other interval was associated with double crossovers. Very high interference was also found on an autosome during oogenesis, implying that each chromosome has only one crossover during oogenesis. During spermatogenesis, recombination on this autosome was reduced by approximately 30% compared to oogenesis, but the relative distribution of the residual crossovers was only slightly different. In contrast to previous results with other autosomes, no double crossover chromosomes were observed. Despite an increased frequency of nonrecombinant chromosomes, segregation of a nonrecombinant autosome during spermatogenesis appears to occur normally. This indicates that an achiasmate segregation system helps to ensure faithful disjunction of autosomes during spermatogenesis.
减数分裂过程中交叉的数量和位置的调控对于正常染色体分离至关重要。我们利用序列标签位点多态性来研究秀丽隐杆线虫卵子发生过程中X染色体上所有交叉的分布，以及卵子发生和精子发生过程中一条常染色体上交叉的分布。在卵子发生过程中，X染色体基本上只有一次交叉，在220条重组X染色体中只有三个可能的双交叉例外情况。所有这三个例外情况中，两个交叉之一都在相同的染色体区间内，这表明该区间内的交叉不会产生干扰。没有其他区间与双交叉相关。在卵子发生过程中，常染色体上也发现了非常高的干扰，这意味着在卵子发生过程中每条染色体只有一次交叉。在精子发生过程中，这条常染色体上的重组与卵子发生相比减少了约30%，但剩余交叉的相对分布仅略有不同。与之前对其他常染色体的研究结果不同，未观察到双交叉染色体。尽管非重组染色体的频率增加，但在精子发生过程中，非重组常染色体的分离似乎正常发生。这表明无交叉分离系统有助于确保精子发生过程中常染色体的忠实分离。
