Hanging on to your homolog: the roles of pairing, synapsis and recombination in the maintenance of homolog adhesion

Homologous chromosomes initially undergo weak alignments that bring homolog ous sequences into register during meiosis. These alignments can be facilit ated by two types of mechanisms: interstitial homology searches and telomer e-telomere alignments. As prophase (and chromatin compaction) proceeds, the se initial pairings or alignments need to be stabilized. In at least some o rganisms, such as Saccharomyces cerevisiae and S. pombe, these pairings can apparently be maintained by the creation of recombination intermediates. I n contrast, synapsis during zygotene may be able to facilitate and/or maint ain chromosome pairing even in the absence of exchange in several higher or ganisms. It thus seems possible that the synaptonemal complex plays a role both in maintaining homolog adhesion during meiotic prophase and, more spec ulatively, in facilitating meiotic exchange.