THE DELAYED ORIGIN OF MUTANTS INDUCED BY EXPOSURE OF EXTRACELLULAR PHAGE T4 TO ETHYL METHANE SULFONATE

Abstract

Mutants induced by exposure of extracellular phage T4 to ethyl methane sulfonate are found in mixed clones; i.e., the treated phage individuals that have mutant descendants also have nonmutant descendants. Several underlying mechanisms of induced mutation that could generate mixed clones are considered and evaluated. The relative proportions of mutants and non mutants in the mixed clones do not correspond to a simple segregation from phage that contained an extracellularly mutated gene and a nonmutant allele. The number and the frequency distribution of these mutants indicate that a mutant clone may be initiated with an equal probability in any generation of vegetative phage growth. Two alternative explanations are offered delay reproduction of a mutated allele, and delayed mutation. The latter hypothesis implies than an alteration has occurred that causes mutation to occur during subsequent reproduction.