Genes involved in the control of nuclear fusion during the sexual cycle of Saccharomyces cerevisiae.

Mutants of Saccharomyces cerevisiae defective for nuclear fusion have been isolated. Their mutations have been characterized by meiotic analysis, dominance-recessivity and complementation. Twelve of the mutations are allelic to the previously described kar 1-1; five affect a second gene designated KAR 2 and three affect a third gene designated KAR 3. There is evidence suggesting that other two mutants are affected in a gene different from the three mentioned. Mutations in KAR 1 and KAR 2 genes are recessive and do not cause obvious effects other than the failure of the karyogamy. Mutations in KAR 3 are semidominant and do cause pleiotropic effects affecting both a mitosis and meiosis.