Comparison of genomes of closely related phages phi 29, phi 15 and PZA using a rapid method of parallel physical mapping

The DNAs of phages phi 29, phi 15 and PZA of Bacillus subtilis were analysed with restriction enzymes EcoRI, HpaI and HindIII. A method was used which permits parallel physical mapping of all three phages, from both ends of their linear genomes. The method is based on transfer of partially digested DNA to DBM paper and sequential hybridization with labelled terminal fragments. It follows from the comparison of the physical maps that phages phi 29, phi 15 and PZA are closely related and that they probably have arisen from a common ancestor by accumulation of point mutations.