Photoreactivation of Ultraviolet Induced Reciprocal Recombination, Gene Conversion and Mutation to Prototrophy in Saccharomyces cerevisiae

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Abstract
Strains of Saccharomyces cerevisiae heteroallelic for the adenine-2 locus, heterozygous for outside markers and homozygous for tryptophan-1; were ultraviolet (u.v.)-irradiated and the effect of post-treatment with white light determined. Mitotic gene conversion to adenine independence and mutation to tryptophan independence and to adenine independence were both decreased by post-u.v.-irradiation treatment with white light, whereas mitotic reciprocal recombination of outside markers was unaffected. The effect of varying the treatment with white light after a constant degree of exposure to u.v.-radiation produced a decrease in reversion frequency to a constant value at light exposures of 5 min. and more. The differing responses of reciprocal recombination and gene conversion are discussed.