The Replication of DNA: I. Two Molecular Classes of DNA

Two classes of DNA have been distinguished on the basis of their reaction to heating in cesium chloride. DNA from proliferating sources is cleaved in half by such treatment, whereas DNA from non-proliferating sources is unaffected in molecular weight. This has been shown by two independent techniques. The relationship between the molecular units produced by cesium chloride treatment and the units conserved during DNA replication is discussed.