The Influence of Oxygen on the Survival and Yield of DNA Double-strand Breaks in Irradiated Yeast Cells

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Abstract
Survival and induction of DNA double-strand breaks were studied in cells of Saccharomyces cerevisiae irradiated under oxic or anoxic conditions with 30 MeV electrons. A linear relationship between DNA double-strand breakage and dose was found in both cases. The o.e.r.[O2 enhancement ratio]-value for colony forming ability was 1.9 .+-. 0.2, whereas the o.e.r.-value for DNA double-strand breakage was 3.0 .+-. 0.1. These results are not inconsistent with the idea that DNA double-strand breaks are involved in killing of yeast cells. The frequency of induction of DNA double-strand breaks was 0.74 .times. 10-11 double-strand breaks per g/mol per Gy when cells were irradiated under O2 and 0.24 .times. 10-11 double-strand breaks per g/mol per Gy under N.