Phenotypic reversion by hydroxylamine. A new group of suppressible phage T4 rII mutants.

ONHERITABLE repair of a mutant phenotype resulting from errors in translation was first described by BENZER and CHAMPE (1961) for rZZ mutants of phage T4. These mutants are ordinarily unable to grow on Escherichia coli strain KB, but can grow on strain B. Treatment of infected KB cells with 5-fluorouracil (5FU) resulted in a large increase in phage yield with certain rZZ mutants, yet the progeny retained the rZZ genotype. CHAMPE and BENZER (1962) suggested that 5FU replaces uracil (U) at the mutated site in the mRNA, and sometimes acts like cytosine (C) during translation, thus correcting the original mutation. The present study deals with a class of rZZ mutants which show phenotypic reversion when treated in vivo with hydroxylamine (HA). Treatment of some other rZZ mutants in vitro by HA induces genotypic reversion (CHAMPE and BENZER 1962). However, the mutants described here do not show genotypic reversion following in vivo treatment with HA.