Multiple Length DNA Molecules of Bacteriophage φX174

Rush and Warner have suggested that circular double length DNA molecules of bacteriophage S13 arise during genetic recombination, presumably in a single reciprocal recombination event between two monomeric circles. In other systems, however, circular molecules of multiple length are produced by errors in replication. We now demonstrate that most circular multiple length DNA molecules of bacteriophage φX174 arise by replication and that, moreover, some catenated DNA molecules contain interlocked rings of two different parental types