GENETICS AND PHYSIOLOGY OF BACTERIOPHAGE T7

Nineteen genes have been identified in T7 by isolation and characterization of amber mutants. Representative mutants from each gene have been ordered on a linear genetic map by means of two-factor crosses, and the genes are numbered in order from left to right. At present, the map is over 200 map units long. From studies of T7-directed protein synthesis (Studier and Maizel, 1969), it is estimated that not more than another 10 or so genes remain to be discovered. The ability of mutants from each gene to synthesize DNA, lyse the culture, and make DNA-containing particles in the restrictive host, E. coli B, has been determined. Mutants from genes 1-6 (at the left end of the map) are defective in both DNA synthesis and lysis; both functions appear to be essentially normal in mutants from genes 7-19. Mutants in genes 7, 11, 12, 13, and 17 can produce noninfectious, DNA-containing particles when grown on B. It appears that in T7 (as in T4 and lambda) related functions tend to cluster along the genetic map. The development of detailed genetic analysis for T7, together with the simplicity of its physical chemistry, makes this system a very attractive one in which to study a number of biological problems at the molecular level. © 1969.