EcoRI restriction endonuclease cleavage site map of bacteriophage P22DNA.

‘l’l~e SWYW EcoKI restriction endonuclease cleavage sites in bacteriophage P%d DNA have been mapped. The cleavage site map of circularly permut.ed P22 linear DNA is a circle. The positions of EcoRI sites in the early region of the P22 genomc were determined by comparing products of EcoRI digestion of maturtx liaear P22 chromosomes with the EcoRI cleavage fragments of DNA of three XimmP22 hybrid phages and a P22 deletion mutant. An EcoRI site in the late region was mapped by partial digestion of the P22 deletion mutant DNA. Since the P22 genes included in the himmP22 hybrid phages, and the genet.ic region missing in the P22 deletion mutant are known, some P22 genes can be positioned on this init,ial physical map of the P22 genome relative to EcoRI cleavage sites.