Gene function and strand breaks in DNA of γ-irradiated T7 bacteriophages

SummaryThe effect of γ-irradiation on gene function in bacteriophage T7 was examined and compared with the alteration of the DNA structure. An early function tested was the synthesis of T7 specific RNA polymerase. Its relative radiosensitivity is 0·32 compared with the plaque-forming ability. The same relative sensitivity of 0·30 was observed for the inhibition of injection and for the formation of double-strand breaks. This observation confirms the hypothesis that, after infection with γ-irradiated phage, only DNA molecules with an intact double helix are injected into the host cell. The radiosensitivity of the synthesis of lysozyme, tested as late function, is 0·58 compared with plaque-forming ability.