Meiotic recombination proceeds via binding of RPA, RAD51, and DMC1 to single-stranded DNA (ssDNA) substrates created after formation of programmed DNA double-strand breaks. Here we report high-resolution in vivo maps of RPA and RAD51 in meiosis, mapping their binding locations and lifespans to individual homologous chromosomes using a genetically engineered hybrid mouse. Together with high-resolution microscopy and DMC1 binding maps, we show that DMC1 and RAD51 have distinct spatial localization on ssDNA: DMC1 binds near the break site, and RAD51 binds away from it. We characterize inter-homolog recombination intermediates bound by RPA in vivo, with properties expected for the critical displacement loop (D-loop) intermediates. These data support the hypothesis that DMC1, not RAD51, performs strand exchange in mammalian meiosis. RPA-bound D-loops can be resolved as crossovers or non-crossovers, but crossover-destined D-loops may have longer lifespans. D-loops resemble crossover gene conversions in size, but their extent is similar in both repair pathways.

减数分裂重组通过RPA，RAD51和DMC1与形成程序化的DNA双链断裂后产生的单链DNA（ssDNA）底物的结合而进行。在这里，我们报告了减数分裂中RPA和RAD51的高分辨率体内图，使用基因工程杂交小鼠将它们的结合位置和寿命映射到单个同源染色体。连同高分辨率显微镜和DMC1结合图，我们显示DMC1和RAD51在ssDNA上具有独特的空间定位：DMC1在断裂位点附近结合，而RAD51与其结合。我们表征体内RPA绑定的同源重组中间体，具有临界位移环（D环）中间体的特性。这些数据支持DMC1而非RAD51在哺乳动物减数分裂中进行链交换的假设。可以将RPA绑定的D循环解析为交叉或非交叉，但以交叉为目标的D循环的寿命可能更长。D环的大小类似于交叉基因转换，但在两个修复途径中其程度均相似。