Chemical mutagenesis and DNA synthesis in cdc8, a DNA replication mutant of Saccharomyces cerevisiae.

Incubation of cdc8 mutants of the yeast Saccharomyces cerevisiae in YPD under permissive conditions, when DNA replication is taking place, prior to transfer to restrictive conditions, strongly stimulates induction of cdc+ colonies of ethyl methane sulphonate (EMS)- and methyl methane sulphonate (MMS)-treated yeast strains HB23 (cdc8-1/cdc8-3), HB26 (cdc8-3/cdc8-3) and HB7 (cdc8-1/cdc8-1). After diepoxybutane (DEB) treatment, both the induction of cdc+ colonies and their stimulation after incubation in YPD under permissive conditions is low. The results obtained show that stimulation of induction of cdc+ colonies under permissive conditions occurs not only after UV-treatment, but also after treatment with such mutagens as EMS and MMS.