Developmental Biology Program, Howard Hughes Medical Institute, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, New York, USA.
Ann N Y Acad Sci. 2012 Sep;1267:95-102. doi: 10.1111/j.1749-6632.2012.06595.x.
Meiotic crossover (CO) recombination involves a reciprocal exchange between homologous chromosomes. COs are often associated with gene conversion at the exchange site where genetic information is unidirectionally transferred from one chromosome to the other. COs and independent assortment of homologous chromosomes contribute significantly to the promotion of genomic diversity. What has not been appreciated is the contribution of another product of meiotic recombination, noncrossovers (NCOs), which result in gene conversion without exchange of flanking markers. Here, we review our comprehensive analysis of recombination at a highly polymorphic mouse hotspot. We found that NCOs make up ∼90% of recombination events. Preferential recombination initiation on one chromosome allowed us to estimate the contribution of CO and NCO gene conversion to transmission distortion, a deviation from Mendelian inheritance in the population. While NCO gene conversion tracts are shorter, and thus have a more punctate effect, their higher frequency translates into an approximately two-fold greater contribution than COs to gene conversion-based allelic shuffling and transmission distortion. We discuss the potential impact of mammalian NCO characteristics on evolution and genomic diversity.
减数分裂交叉（CO）重组涉及同源染色体之间的相互交换。CO 通常与交换位点的基因转换有关，在交换位点上，遗传信息从一条染色体单向转移到另一条染色体。CO 和同源染色体的独立分配对促进基因组多样性有重要贡献。尚未被认识到的是减数分裂重组的另一种产物——非交叉（NCO）的贡献，它导致基因转换而不交换侧翼标记。在这里，我们回顾了我们对高度多态性小鼠热点的重组的综合分析。我们发现，NCO 约占重组事件的 90%。一条染色体上优先的重组起始使我们能够估计 CO 和 NCO 基因转换对传输扭曲（种群中偏离孟德尔遗传的现象）的贡献。虽然 NCO 基因转换片段较短，因此影响更具点状，但由于其频率较高，与 CO 相比，它们对基于基因转换的等位基因改组和传输扭曲的贡献大约高出两倍。我们讨论了哺乳动物 NCO 特征对进化和基因组多样性的潜在影响。
