Inducibility of gene conversion in Saccharomyces cerevisiae treated with MMS.

At high survival levels (85%), point mutation and gene conversion frequencies were determined in strain D7 of Saccharomyces cerevisiae after treatment with methyl methanesulfonate (MMS) either after cells were incubated in complete medium before plating or following a split-dose protocol. It is shown that induction of gene conversion by MMS post-incubation leads to an additional enhancement in frequency. This increase is not observed for point mutation. By fractionation of the MMS dose (1 mM + 1 mM) with incubation in complete medium between the 2 doses the frequency of gene conversion is twice as high as with a single equal total dose (2 mM). This treatment does not modify the frequencies of point mutation. These data support the notion that an inducible recombinogenic function exists in wild-type yeast.