FREQUENCY OF DELETIONS AMONG SPONTANEOUS AND INDUCED MUTATIONS IN SALMONELLA

Abstract

The cysC locus of Salmonella typhimurium was selected for a comparative study of frequencies of deletion mutants among spontaneous, 2-aminopurine-induced, and ultra-violet-induced mutants of strain LT-2, and spontaneous mutants of strain LT-7. In strain LT-2 the spontaneous and UV-induced mutations included about 40% deletions whereas none were found among 40 mutations induced by 2-aminopurine. In strain LT-7, the frequency of deletions among spontaneously occurring mutations was low. Apparently, both spontaneous and UV-induced mutations result from deletions and single-site mutations but that 2-aminopurine and mutator genes affect only the mechanism that produces single-site mutants.