Correlation of gamma-ray inactivation and strand scission in the replicative form of phi-X174 bacteriophage DNA.

An important feature of the inactivation of double-stranded DNA viruses is that one radiochemical lesion induced in the DNA by ionizing radiation, radio- active decay of p32 atoms, or ultraviolet light can alone inactivate their reproductive ability, but its efficiency in causing this end point is much less than one.'Thus, these viruses can sustain numerous sublethal hits.For the case of X-rays and y-rays, it has been reported for two systems2 3 that double-strand scission is the lesion correlating with lethality, the reason for the low killing efficiency being that this lesion occurs at a lower frequency than other types of lesions.It may be assumed that this explanation applies generally.However, the work reported earlier4 on double-stranded RF-DNA of 4X174 bacteriophage, in which it was observed that the killing efficiency of X-or Byrays is 0.25 compared to 0.05 for T4