Effects of p-fluorophenylalanine on the induction of mutations in bacteriophage T4 II. Nitrous acid mutagenesis

Abstract

The effects of p -fluorophenylalanine (PFPA), an analogue of phenylalanine (PHE), on the potency and the specificity of nitrous acid (NA) mutagenesis in the r system of bacteriophage T4 were measured. 1. (a) Forward mutation The frequencies of NA-induced r mutants were approximately doubled when mutagenized phage infected E. coli B in the presence of the analogue compared to controls where PHE was substituted for PFPA, or where no amino acid was added. The spontaneous forward mutation frequency was not affected by the analogue, nor was the specificity of the NA mutagenesis. 2. (b) Reverse mutation The frequency of spontaneous and NA-induced reversion of an rII transition mutant was unaffected by PFPA if the phage were plated direct on the restrictive host after mutagenesis. However, if mutagenized phage were first allowed a cycle of growth in the presence of PFPA the induced reversion frequency was increased about 3-fold compared to the control.