Mutagenesis in cdc7 strains of yeast. The fate of premutational lesions induced by ultraviolet light.

cdc7-1 cells bearing UV-revertible mutations are virtually immutable by all means so far tested. By mating UV treated cdc7-1 cells with untreated cdc7+ cells carrying the same revertible alleles it is possible to rescue premutational lesions as revertants and to study their fate in cdc7-1 cells. If storage intervenes between treatment and mating there is a rapid decline in revertants rescued. This is not related to the death of cdc7-1 cells with storage nor does it reflect a progressive loss in their ability to mate.