Comparison of DNA-copying fidelity during repair and semiconservative synthesis by radioactive precursor distribution analysis

Abstract

The authors compare the fidelity of DNA copying during semiconservative and reparative synthesis under normal conditions and during cortisol-induced activation of free-radical processes, by examining the distribution of radioactivity among DNA pyrimidine isopliths. Radioactivity of nucleotide material in the isopliths was measured by counting in appropriate zones of the chromatograms in toluene scintillator. The investigation shows that injury to DNA of different organs, both directly and as a result of faulty repair, leads to shortening of the pyrimidine isopliths, i.e., to changes in the primary structure of DNA. These data help to explain the simultaneously cytostatic, carcinostatic, and mutagenic action of irradiation, cortisol and hydroxyurea.