[Autoradiographic analysis of molecular mechanisms of differential staining of sister chromatids]

The significance of procedures involved in the technique of differential staining of sister chromatids is estimated by quantitative autoradiography. Photolysis of bromodeoxyuridine-substituted DNA is shown to be the main process determining the quality of differential staining under certain experimental conditions. On the basis of modes provoking DNA degradation and washing DNA fragments off the chromosomes, a simplified method including only irradiation of chromosomes under a mercury lamp and treatment with a sodium citrate solution is proposed.