DNS-Syntheseraten einer strahlensensiblen Saccharomyces-Mutante nach UV- oder Röntgenbestrahlung / Rates of DNA Synthesis in a Radiation-sensitive Saccharomyces Mutant after UV or X-Ray Irradiation

Abstract

The incorporation of thymidine-2-¹⁴C-monophosphate (TMP) after UV and X-ray irradiation in two diploid Saccharomyces strains with different radiation sensitivities of colony-forming ability was measured to determine the rate of DNA synthesis. The sensitive strain was homozygous for a gene causing UV and X-ray sensitivity (r⁸ ₁ r⁸ ₁ ) whereas the resistant strain was homozygous for the corresponding wild type alleles (++). The TMP-incorporation was measured for a period of three hours either immediately after irradiation or after an intervall of 3 or 6 hrs. in nutrient medium without radioactive TMP. The dose effect curves obtained were generally biphasic with a steep slope at low doses and with a shallow slope at high doses. The values obtained for the r⁸ ₁ r⁸ ₁ -strain were significantly lower than those of the + + -strain. The difference in the rate of DNA-synthesis increased with increasing interval between the time of irradiation and the time of application of TMP.