9507089 Dresser The long-range goal of this work is to understand how meiosis-specific structures, such as synaptonemal complexes and recombination nodules, are organized and function in meiotic chromosome repair, recombination and segregation. It has been shown that alterations in the stoichiometry of subunits in multicomponent structures can perturb the function of those structures. As a novel first step toward identifying the components of the meiosis-specific structures in the yeast Saccharomyces cerevisiae, cells have been challenged with wild-type yeast DNA carried on plasmids that replicate to 100 or more copies per cell. A sensitive assay for meiotic chromosome nondisjunction has made it possible to identify plasmids carrying inserts that specifically cause errors in meiotic chromosome segregation or prevent the completion of meiosis. Forty-one such plasmids carrying different inserts have been found. Preliminary results indicate that some of the plasmids contain meiotic genes previously identified from recessive mutant hunts; other plasmids contain novel genes, some of which are likely to have been missed in previous searches due to functional overlaps with other genes. Identification of genes in the latter class is particularly timely given the impending completion of the yeast genome sequence, which will greatly facilitate analysis of the functions of families of genes. The work proposed here is (1) to conduct secondary screens on the plasmid collection to identify genes most likely to be directly involved in meiotic chromosome segregation, and (2) to perform immunocytological studies on a subset to identify gene products that are components of meiotic chromosome structures. %%% By identifying and analyzing novel genes and functions required for chromosome repair, recombination and segregation in meiosis, these studies in the yeast model system will contribute to an understanding of how cells in eukaryotes, including humans, keep their genomes intact during this critica l period in the reproductive cycle of sexual organisms. Errors in meiosis can result in cells of the next generation having an abnormal number of chromosomes or in cell death. ***
