DNA repair kinetics after exposure to X-irradiation and to internal beta-rays in CHO cells

DNA strand breaks induced by X- or internal beta-rays were measured using the alkaline unwinding technique. For either type of radiation, repair kinetics were found to be best described by three exponential components, the half-times of which are 2 min, 17 min and 200 min, respectively. These values are the same for X- and internal, beta-irradiation but the initial fractions of the components are different.