Genetic effects of formaldehyde in yeast. II. Influence of ploidy and of mutations affecting radiosensitivity on its lethal effects

Abstract Haploid and diploid cells of Saccharomyces cerevisae have the same sensitivity to formaldehyde, exponentially growing cells being more sensitive than stationary phase cells for both degrees of ploidy. Strains defective ( rad 1–3 ) or with a reduced capacity g9 − , cytoplasmic respiratory deficient mutants) in excision rapair of ultraviolet-induced pyrimidine dimers show a greater sensitivity to formaldehyde than the corresponding wild type. A mutant defective in radiation-induced gene conversion ( rec5 ) shows the same sensitivity as the wild-type strain. It appears that the excision-repair system plays and important role especially in stationary phase cells, in repairing a fraction of formaldehyde-induced lesions.