Construction of an accurate map of the sites where restriction endonucleases cleave DNA—restriction mapping—is critical for almost all subsequent manipulations of genetic material. Restriction mapping is based upon the cleavage of DNA at or near specific nucleotide sequences with restriction endonucleases and the determination of the sizes of the resulting DNA fragments by gel electrophoresis (...

Characterization of eight restriction endonucleases isolated from five strains of Herpetosiphon giganteus is described. HgiCI from strain Hpg9 recognizes and cleaves the degenerate sequence: GGPyPuCC, producing 5'-hexanucleotide protruding ends. Endonucleases HgiBI, HgiCII and HgiEI are isoschizomers of AvaII; HgiCIII and HgiDII are isoschizomers of SalI; and HgiDI and HgiGI are isoschizomers o...