Radiation-Induced Reversion of Transition Mutants

Abstract

X-irradiation increased the reversion frequency of two transition mutants of Escherichia coli, one of which (meth-) differed genetically from wild type by an adenine-thymine substitution of a guanine-cytosine base pair, the other (urg-2-) by a guanine-cytosine substitution of an adenine-thymine base pair. The lethal effects of the radiation were greatest when protein synthesis was prevented for a period immediately after irradiation. A period of 30 min at 37°0 was as effective as 22 hr. Irradiation of a saline suspension gave a lower survival of 0·2 times that of bacteria irradiated after being spread on minimal agar plates.