Investigation of the interaction of uv and ionizing radiations in the combined irradiation of diploid yeast strains with different radiosensitivity

Combination experiments were made with three diploid yeast strains of different radiosensitivity in order to investigate the interaction of ionizing and nonionizing radiations. The strains used are the wild strain 211 and the two radiosensitive mutants S 2,094 and S 2,095. The results obtained show that interactions do occur: pre-irradiation with ionizing radiations reduces the uv plateau in the wild type, but it is not completely leveled down. In another strain, which is assumed to be recombination-negative, the uv plateau disappears completely after pre-irradiation with x-rays and alpha rays; in an excision- negative strain, however, irradiated under the same conditions, almost no interaction at all could be detected. From these results it is concluded that the x-ray/uv-light interaction occurs during excision repair and that the recombination system remains effective, regardless of the type of irradiation that induced the damage. (GE)