Alterations of liver DNA after x-irradiation. Reassociation and hybridization with nuclear RNA

When RNA is extracted either from irradiated or unirradiated rat livers, no difference in its ability to hybridize with DNA is detectable. In contrast, the ability of DNA extracted from irradiated animals to hybirdize with RNA is decreased, probably as a result of DNA fragmentation. Sedimentation of X-irradiated DNA on sucrose gradients separates a small (low molecular weight) from a large peak (high molecular weight). The hybridization capacity for RNA of the large molecular weight DNA is similar to that of unirradiated DNA, but that of the small molecular weight is DNA reduced. After irradiation of the denatured DNA in vitro, the reassociation of DNA is inhibited, which suggests that DNA strands have lost part of their complementariness.