RED1: a yeast gene required for the segregation of chromosomes during the reductional division of meiosis.

A mutation at the RED1 locus was identified in a search for sporulation-proficient, meiotic-lethal yeast mutants. The few viable spores produced in the red1-1 mutant are highly aneuploid, suggesting that the spore lethality results from a high frequency of chromosome nondisjunction. Disomic spores produced by the red1-1 mutant contain nonsister chromatids and the red1-1 spore inviability phenotype is alleviated in red1-1 spo13 double mutants; these results indicate that nondisjunction occurs at the first meiotic division. The red1-1 mutant is recombination-proficient. The RED1 gene was cloned by complementation of the meiotic lethal phenotype; strains carrying a disruption of the gene are mitotically viable. We propose that the RED1 gene product is involved in meiosis I chromosome disjunction, perhaps by maintaining the connections between homologous chromosomes through metaphase I.