The different pathways involved in meiotic recombination in mammals

尽管不清楚Mnd1基因敲除小鼠是否与Hop2小鼠有本质上的不同，但现在已经清楚的是，这些小鼠是哺乳动物减数分裂遗传信息的宝库。与Hop2小鼠不同，Mnd1小鼠有相当比例的精母细胞核显示同源配对染色体突触，进展到粗成期晚期，但没有显示任何交叉。这些结果强烈表明，正如对出芽酵母提出的那样，小鼠双链断裂的修复有两种主要途径（一种导致交叉和非交叉，另一种导致非交叉），而Hop2可以作用于这两种途径。这只小鼠也可能提供关于染色体相互作用主要是如何在同系物和姐妹之间进行的见解，这是导致交叉的基本要求，确保染色体的适当分离。

Although it was not clear that Mnd1 knockout mice would be substantially different from Hop2 mice it has now become clear that these mice are a treasure trove of genetic information about mammalian meiosis. Unlike the Hop2 mice, the Mnd1 mice have a significant proportion of spermatocyte nuclei that show homologously paired chromosome synapsis, progress up to late pachytene but do not show any crossovers. These results strongly suggest that, as has been proposed for budding yeast, there are two main pathways for the repair of double-strand breaks in mice (one that leads to both crossover and non-crossovers and one that results in non-crossovers exclusively) and that Hop2 can act on both pathways. This mouse might also provide insights into how chromosome interactions are channeled primarily between homologs versus sisters, a fundamental requirement leading to the crossovers that ensure the proper segregation of chromosomes.