MUTATIONS INDUCED BY ULTRAVIOLET LIGHT WITHOUT ATTENDANT LETHALITY

Abstract
Mutations could be induced in bacterial populations by doses of UV light so small that there was no measurable decrease in the number of viable cells following irradiation. Mutations to streptomycin resistance induced by such UV doses can be photoreversed only for a short period of time following UV treatment. The delay in the phenotypic expression of mutants was markedly dependent upon the dose of radiation.