FUNCTIONS OF 2 GENES IN FIRST-STEP-TRANSFER DNA OF BACTERIOPHAGE T5

Bacteriophage T5 transfers initially an 8 to 8.5% portion of its DNA molecule-the FST-DNA† † Abbreviation used: FST-DNA, first-step-transfer DNA.-to a host cell. Further transfer occurs only under conditions which permit protein synthesis. Two functions seemed attributable to the FST-DNA: degradation of the host DNA, and synthesis of one or more proteins required for complete transfer of phage DNA to host cell. Mutants in one out of six tested genes were assigned to the FST-DNA. This paper describes the isolation of additional amber mutants in two genes of the FST-DNA (genes I and II), and of temperature-sensitive mutants in gene I. Mutants in gene I can neither degrade the host DNA, nor complete the transfer of their DNA under non-permissive conditions. Mutants in gene II can degrade the DNA of a non-permissive host, but fail to transfer more than their FST-DNA. These results confirm genetically and biochemically the specificity of the FST-DNA and two of its functions in the viral growth cycle. © 1969.