Influence of Oxygen on the Induction of Mutations in Bacteriophage ΦX174 by Ionizing Radiation

Abstract
Several mutants of bacteriophage ΦX174 having nonsense codons in different cistrons are reverted with a higher efficiency to pseudo wild-type particles, i.e. particles able to propagate in suppressorless host bacteria, when irradiated with γ-rays in the presence of oxygen than when irradiated under anoxic conditions. For an ochre mutant of ΦX174 it was found that the radiation-induced conversion into an amber mutant, which corresponds with a transition of adenine in the parental DNA into guanine in the progeny DNA, is enhanced by oxygen. Differences between amber mutants of more than two-hundred fold in the efficiency of induction of pseudo wild-types show that the local environment of the amber codon in the phage particle exerts a great influence on the induction.

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