(Left) In wild-type oocytes, Mei-P22, which localizes to discrete foci prior to the time γH2AV foci are present, is located at chromatin adjacent to the SC (Liu et al., 2002). Vilya localizes to the central region of the SC and is required along with its binding partner, Mei-P22, and Mei-W68 (the Spo11 homolog) for formation of DSBs. Although initially Vilya may localize to a vast majority of, if not all, DSBs, as the oocytes mature into early/mid-pachytene, Vilya is retained and/or recruited to form discrete foci at sites of crossing over. Failure to accumulate Vilya at DSB sites would direct that DSB to a noncrossover fate. (Right) In the absence of Mei-P22 or Mei-W68, and thus in the absence of DSB formation, Vilya fails to localize to discrete foci and is found exclusively along the central region of the SC. In the absence of Vilya, we speculate, based on the fact that Mei-P22 can localize to discrete foci in the absence of Mei-W68 (Liu et al., 2002), that Mei-P22’s localization is unaffected. However, DSB formation would fail due to the absence of vilya function. In the absence of Mei-W68, Mei-P22 is able to bind normally (Liu et al., 2002), however, due to the absence of DSBs, Vilya does not form discrete foci. In all these instances, crossovers do not form.