Combined mutagenic action of chemicals and radiation in diploid yeast.

The interaction between the mutagenic action of chemicals and radiation was studied by using a diploid yeast strain Saccharomyces cerevisiae BZ 34 with mitotic gene conversion as the end-point. The cells were treated with EMS, MMS or 4-NQO alone or in combination with gamma-radiation. The 2 alkylating agents EMS and MMS produced an additive mutagenic response, whereas 4-NQO exhibited an antagonistic effect in the combined treatment with gamma-radiation.