Class of phi chi 174 mutants relatively deficient in synthesis of viral RNA.

Nonpermissive cells infected with phiX174 gene D amber mutants synthesized some sixfold less viral RNA than permissive cells. The decrease was unaffected by increasing the multiplicity of infection and was a consequence of an overall decrease in all viral RNA species. It is suggested that the gene D product may function in replicative form DNA unwinding to expose the template for transcription.