[Physical map of the DNA of bacteriophage tf of Pseudomonas putida]

A physical map has been constructed for P. putida bacteriophage tf DNA containing single-strand breaks (nicks). Localization of cleavage sites for EcoRI, HindIII, HpaI ClaI, BamHI, SalI, XbaI and XhoI restriction endonucleases was determined. Position of single-strand breaks was mapped by electrophoretic analysis of denatured tf DNA and electron microscopy of partially denatured DNA samples. The tf genome is characterized by the presence of two classes of nicks differing in the frequency of their presence in population of bacteriophage DNA molecules.