G. Shirleen Roeder

My lab studies meiosis, using budding yeast as a model system. We have focused on the interactions between homologous chromosomes that occur during meiotic prophase and ensure the proper segregation of chromosomes at the first meiotic division. These interactions include homolog pairing, chromosome synapsis (i.e., synaptonemal complex assembly) and genetic recombination. We have demonstrated roles for telomeres and for centromeres in the pairing of homologous chromosomes. Our studies have identified genes that encode building blocks of the synaptonemal complex, the proteinaceous structure that holds homologous chromosomes close together along their lengths during mid-meiotic prophase. We have also identified a complex of proteins involved in the initiation of chromosome synapsis and shown that centromeres are preferred sites for synapsis initation early in meiotic prophase. We have used mutations in genes encoding synaptonemal complex proteins to investigate the role of the complex in crossing over, chromosome segregation and the proper distribution of meiotic recombination events. Our work has identified two distinct pathways of meiotic recombination and characterized a mechanism that inhibits the mitotic recombination machinery in meiotic cells. We have also identified and characterized components of the cell cycle checkpoint that prevents exit from meiotic prophase until meiotic recombination has been completed.