Abstract
Amber mutants of bacteriophage T5 defective in gene C2 have been characterized. The product of this gene is required for the normal turn-on of synthesis of late RNA's and proteins, and, apparently, for the normal continued synthesis of early RNA's and proteins during late stages of infection. The inability of nonpermissive cells to synthesize any proteins, either late or early, during the late period after infection with a C2-mutant is not due to premature lysis of the infected cells, to a depletion of the cellular energy supply, or to degradation of phage DNA at late times. A possible role for the product of gene C2 in early and late transcription of the viral genome is suggested.