Meiotic Recombination Mechanism

Mechanism of meiotic recombination
The Meiotic recombination is an integral part of the meiotic division in most eukaryotes. It can lead to either crossovers (reciprocal exchange of genetic material between homologous chromosomes), or non-crossovers (non-reciprocal exchange of the genetic material). In eukaryotes, only a small percentage of meiotic DSBs result in crossover products (Sung et al., 2003; Youds and Boulton, 2011). In contrast, repair of DSBs in the mitotic cells happen mostly through the non-crossover recombination pathway, via the sister chromatids. Meanwhile the meiotic cells have an innate barrier to sister chromatid repairing and hence, they use the invasion of one chromatid of the homologues for repairing (Niu et al., 2005).

The synaptonemal complex is a protein complex, which can mediate the crossing over among homologous chromosomes (Peoples,T.L. 2002). It consists of three important parts, the lateral element, the central element and the transverse element. During the leptotene stage, the SYCP2 and SYCP3 proteins form axial elements, lateral element and precursors. The SYCP1 protein contains a carboxy-terminal domain and an amino-terminal domain that are necessary for interaction with lateral and central elements, respectively. The SYCP1 from transverse filaments interact with the SYCE1 and SYCE2, which are the central elements of the synaptonemal complex (Ding, Da‐Qiao,

Moreover, SCC1 can also be replaced by REC8 (Revenkova and Jessberger, 2006). The Rad21-like protein (Rad21L) is a paralogue of the mammalian meiosis-specific SSC1/REC8 (Gutiérrez-Caballero et al., 2011). Uhlmann et al. (2011), reported three distinct classes of meiotic cohesin complexes. The first one has REC8 in the protein complex, while the second and third groups have Rad21L and Rad21Scc1 resectively (Uhlmann, 2011). The Rad21L containing group is thought to act as a foundation for lateral-element formation because only Rad21L recruits SYCP1. When the recombination is complete, Rad21L gets dissociated from the complex as a result of phosphorylation. This dissociation can result in synaptonemal-complex disassembly. Thereafter, the meiotic cohesin complexes containing Rad21Scc1 is bound to the chromosomes (Figure 1.8) (Uhlmann,