The extent of exicision repair of gamma ray damage in E. coli

Ionizing radiation produces a very wide variety of chemical change in DNA. The sensitivity of E. coli cells to gamma radiation is influenced by mutations in known repair genes. In strains that are recombination proficient, sensitivity is reduced and two components are seen, the more resistant being that in which the S.O.S. response is induced. In recombination deficient strains, sensitivity is greater. If, in addition, excision repair (the UvrABC enzymes) or the 3-methyl glycosylase is absent, sensitivity is greater, but not additively so. This suggests that uvrA and alkA affect a common pathway. Thus, a part of gamma ray damage (in the oxygenated condition) appears to be repaired by removal of a damaged base to form an AP site and by subsequent excision repair