Mutator activity of petite strains of Saccharomyces cerevisiae.

Petite strains in Saccharomyces exhibit enhanced spontaneous mutation rates of nuclear genes regardless of whether they are cytoplasmically or nuclearly inherited, or whether or not the cytoplasmic petite strains have mitochondrial DNA. In petite strains, the mutation rate for the nonsense allele lys1-1 is enhanced by a factor of 3-6 and for the missense allele his1-7 by a factor of 2 as compared with their grande counterparts. The reversion of a third allele, the putative frameshift mutation, hom3-10, is not enhanced in a petite background. The results indicate that the spontaneous mutation rate of an organism can be altered by indirect intracellular influences.