Antimutator activity during mitosis by a meiotic mutant of yeast.

Diploids homozygous for the mutation spo7-1 do not exhibit net premeiotic DNA synthesis at 34 degrees C and are defective in commitment to recombination following exposure to sporulation medium. The spo7-1 mutation confers antimutator activity during mitosis at 34 degrees C, indicating that the SPO7 gene product is involved in both mitotic and premeiotic DNA metabolism. Strains bearing spo7-1 are slightly more sensitive to killing by ultraviolet light than the wild type but are proficient in UV induced mutation and mitotic intragenic recombination. The mitotic antimutator activity of spo7-1 is directed against a class of forward mutations known to occur more frequently during mitosis than meiosis.