Comparison of the cytotoxic and mutagenic effects of selected mutagens on excision repair-sufficient and -deficient AD-3 mutants of Neurospora crassa.

The excision repair-deficient genetic marker uvs-2 was crossed into the tester strains N23 and N24 of Neurospora crassa. Comparison was made among the effects of selected mutagens on a repair-sufficient strain (N23 or N24) and a repair-deficient strain (N23 uvs-2 or N24 uvs-2) with regard to cell killing and induction of reverse mutation from adenine dependence to adenine independence. Methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS), 1,2,7,8-diepoxyoctane (DEO), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), 2,3,5,6-tetraethyleneimino-1,4-benzoquinone (TEB) and ICR-170 were found to be more toxic to the repair-deficient strains than to the repair-sufficient strains. For the induction of reverse mutations N23 uvs-2 appeared to be more sensitive than N23 to MNNG and TEB and to the high concentrations of MMS and DEO while N24 was 20 times more sensitive than N24 uvs-2 to ICR-170.