Effect of millimeter waves on UV-induced recombination and mutagenesis in yeast

Effects of millimeter waves (MMW) on cell survival and ultraviolet-induced reciprocal and non-reciprocal recombination and mutagenesis were studied in the diploid D7 strain of the yeast Saccharomyces cerevisiae. MMW exposures lasted for 30 min (0.13 mW cm(-2), 61.02-61.42 GHz) and were followed in 60 min by a 100 J m(-2) dose of 254 nm ultraviolet (UV) radiation. The effect of the exposures was evaluated from the colony-forming ability of the cells on complete and selective media, and from the number of aberrant colonies formed. The MMW pretreatment did not alter cell survival or the frequency of reverse mutations. The incidence of conversions was higher in most cases in the MMW-treated cells (p < 0.05). MMW also increased the scores of crossovers and colored aberrants in isolated experiments, though the average increase for all experiments (performed with different MMW frequencies) was not statistically significant. The results suggested that the MMW irradiation did not alter the UV-induced mutagenesis, but could facilitate recombinagenic processes. (C) 1997 Elsevier Science S.A.