A system selective for yeast mutants deficient in meiotic recombination

Summary An experimental design and rationale for detecting and recovering Saccharomyces cerevisiae mutants specifically blocked in meiotic gene conversion is presented. The system utilizes an otherwise haploid strain disomic (n+1) for chromosome III which is simultaneously heterozygous for the mating-type locus and heteroallelic at leu2. The former is an essential requirement for inducing meiotic development; i.e., DNA replication and sporulation upon transfer to acetate media, while the latter provides a convenient signal for assaying recombination at the intragenic level. Of 940 clones screened qualitatively after mutagenesis with ethyl methanesulfonate, 91 presumptive mutants were isolated. These are classed arbitrarily into four groups according to the reduction in interallelic recombination observed in quantitative tests.Supported by research grants GM: 17317 and GM: 16522 from the National Institutes of Health and a grant from the National Sciences Foundation, GB: 8534.