Ionizing radiation and DNA-chain elongation in ataxia telangiectasia lymphoblastoid cells

DNA-chain elongation rates, determined by sedimentation analysis, were found to be similar in control and ataxia-telangiectasia lymphoblastoid cells. A gamma-radiation dose of 6 Gray, which had previously been shown to have a marked inhibitory effect on initiation of DNA replication, had no appreciable effect on elongation rates in either cell type. Elongation rates were also determined at 20 Gray of gamma-rays by pulsing cells with [3H]thymidine prior to irradiation to avoid anomalous sedimentation behaviour. At this radiation dose elongation was almost completely inhibited in control cells while little or no inhibition was observed in ataxia-telangiectasia cells. Deoxyribonucleoside triphosphate pool equilibration times were not altered at either dose.