Figure 1.

Overview of critical processes during the MI stage. (A) After DNA replication, sister chromatids of both homologous chromosome pairs are held together by multiple units of the cohesin complex. (B) Alignment of the homologous chromosomes is facilitated by the synaptonemal complex. (C) The first step of homologous recombination occurs through the formation of double strand breaks (DBS). This process is Spo-11 dependent, and strand invasion is mediated by the Rad51-DMC1 complex, which is stabilised by Hop2-Mnd1. (D) After homologous recombination, the cohesin complex of the sister chromatids is cleaved by separase along the length of the sister chromatids. Cohesin at the centromeres is protected by shugosin, inhibiting the separase-mediated cleaving. (E) Sister kinetochores connect to microtubules emanating from the same spindle poles, as such separating the newly recombined homologues.