Zetka M C, Rose A M
Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Genetics. 1995 Dec;141(4):1339-49. doi: 10.1093/genetics/141.4.1339.
Meiotic crossovers are not randomly distributed along the chromosome. In Caenorhabditis elegans the central portions of the autosomes have relatively few crossovers compared to the flanking regions. We have measured the frequency of crossing over for several intervals across chromosome I in strains mutant for rec-1. The chromosome is approximately 50 map units in both wild-type and rec-1 homozygotes, however, the distribution of exchanges is very different in rec-1. Map distances expand across the gene cluster and contract near the right end of the chromosome, resulting in a genetic map more consistent with the physical map. Mutations in two other genes, him-6 and him-14, also disrupted the distribution of exchanges. Unlike rec-1, individuals homozygous for him-6 and him-14 had an overall reduction in the amount of crossing over accompanied by a high frequency of nondisjunction and reduced egg hatching. In rec-1; him-6 and rec-1; him-14 homozygotes the frequency of crossing over was characteristic of the Him mutant phenotype, whereas the distribution of the reduced number of exchanges was characteristic of the Rec-1 pattern. It appears that these gene products play a role in establishing the meiotic pattern of exchange events.
减数分裂交叉并非随机分布于染色体上。在秀丽隐杆线虫中，与侧翼区域相比，常染色体的中央部分交叉较少。我们已经测量了rec - 1突变株中跨越染色体I上几个区间的交叉频率。在野生型和rec - 1纯合子中，该染色体大约为50个图距单位，然而，rec - 1中交换的分布非常不同。图距在基因簇中扩大，在染色体右端附近收缩，从而产生一个与物理图谱更一致的遗传图谱。另外两个基因him - 6和him - 14中的突变也扰乱了交换的分布。与rec - 1不同，him - 6和him - 14的纯合个体交叉总量总体减少，同时伴有高频率的不分离现象和降低的卵孵化率。在rec - 1; him - 6和rec - 1; him - 14纯合子中，交叉频率具有Him突变体表型的特征，而减少的交换数目的分布具有Rec - 1模式的特征。看来这些基因产物在建立交换事件的减数分裂模式中发挥作用。
