Effect of X-irradiation on DNA-labelling in Cells Exposed during Synthesis

Abstract

Bean roots were exposed to 140–2500 r x-rays aerobically during a 16–17 min immersion in a solution of thymidine labelled with ¹⁴C or ³H. There was no evidence of increase in the rate of DNA synthesis due to irradiation, nor in the number of cells which became labelled. On the contrary, radiation exposure tended to decrease both these parameters. Appreciable activity remained in the cytoplasm. The amount of cytoplasmic activity not removed by N/1 TCA hydrolysis at 60°c was greater in irradiated than in unirradiated cells.