Changes in properties of DNA caused by gamma and ultraviolet radiation. Dependence of conformational changes on the chemical nature of the damage.

Changes in the pulse-polarographic behaviour and circular dichroism spectra of DNA were investigated after gamma and ultraviolet irradiations and after degradation by DNAse I. It was found that moderate doses of radiation cause local conformational changes in the double helix, which are dependent on the chemical nature of the damage. Only the accumulation of structural changes after high doses of the radiations or after extensive enzymic treatment may cause formation of single-stranded regions in DNA.