DNA newly synthesized in UV irradiated Escherichia coli B/r Hcr+ was 2 min pulse-labeled at various periods, then denatured and analysed by sucrose gradient centrifugation either in neutral or in alkaline conditions. Data indicate that in DNA of damaged cells alkali-labile sites are produced. In cells saturated with inducible proteins production of alkali-labile sites disappears in ∼1 h. In the absence of inducible proteins production of alkali-labile sites continues.
