The influence of the composition of the selective medium on convertogenic activity of ethyl methanesulfonate in Saccharomyces cerevisiae D4.

The frequency of prototrophic recombinants produced by mitotic gene conversion at the trp5 and ade2 loci were observed using the plate test. The yeast cells were exposed in the concentration gradient of ethyl methanesulphonate--EMS (10 microliter/plate). Selective media with addition of a small amount of tryptophan (for the selection of the convertants trp+) or adenine (for the selection of the convertants ade+) were used. The use of medium with addition of tryptophan or adenine considerably increased the sensitivity of the plate method as compared with the use of the medium deficient in either tryptophan or adenine. The above results suggest possible usefulness of testing for mutagenic activity various chemical using growing cells of yeast.