Abstract
DNA polymerase from unpurified extracts of either infected or serumtreated resting mouse embryo cells was bound to double-stranded polyoma DNA and the complex could be separated from the free enzyme and other protein by zone centrifugation through sucrose gradients. Addition of extract to component I (supercoiled) polyoma DNA converted the DNA to a slower sedimenting form, but had little effect on the sedimentation rate of a mixture of components II and III. DNA extracted from the complex formed from extract and component I had properties indicating that both strands of the DNA were unbroken.