Meiotic Chromatin: The Substrate for Recombination Initiation

The DNA double-strand breaks (DSBs) that form during meiosis I prophase initiate recombination. DSBs also play a critical role, in many species, in driving progressive association and colocalization of homologs, which culminate in full homolog synapsis at pachytene. Data from many species indicate that DSBs and recombination are not uniformly distributed, but occur more frequently in some places than in others. Studies from Saccharomyces cerevisiae and Schizosaccharomyces pombe, where DSBs have been mapped at the molecular level, indicate that chromatin structure is an important determinant of where DSBs form, but that other factors are also involved. Less direct data from other species also address possible roles for chromatin structure and higher-order chromosome structure in DSB formation.