Studies on the structure of repllcative intermediates In bacteriophage M13 single stranded DNA synthesis

Pulse-labeled replicative intermediates in M 13 single stranded DNA synthesis can be separated by dye-buoyant density centrifugation into two major fractions: Supercoiled molecules (RI I) containing viral strands of more than one genome length, and "relaxed " molecules (RI II) with labeled DNA chains shorter than unit length. It is postulated that RI II molecules might be formed in vivo by site-specific nicking of RF I molecules