IX. Nucleinsäuregehalt und Nucleinsäuresynthese nach Röntgenbestrahlung

Abstract

The amount of DNA and RNA per dry weight as well as the rate of RNA synthesis was determined in a series of almost isogenic and homozygous Saccharomyces strains of different ploidy which had irradiated with different doses of X-rays. It was found that the RNA content per dry weight showed only a small decrease after irradiation even with high doses. The decrease in the DNA content after irradiation is larger, and it is already maximal at the smallest X-ray dose tested (75 krad) . No further decrease could be observed even after application of 225 krad. The RNA synthesis is much more radioresistant in all strains tested (haploid-hexaploid) than the colony forming ability. X-ray doses which reduce the colony forming ability of the cells to less than 1% lead to a reduction of the RNA synthesis of only about 50 per cent. The inactivation of RNA synthesis increases with increasing irradiation doses and increasing incubation time after irradiation. There was only a small difference in the radiosensitivity of the synthesis of soluble or ribosomal RNA. Genetic effects on the radiation inactivation of the colony forming ability, previously described as “aα-effect” and “AS-effect”, show no influence on the radiosensitivity of cellular nucleic acid content and synthesis.