Chronology of Viral Functions in Bacteriophage α

Abstract

Temperature-sensitive mutants of phage a were subjected to short pulses of permissive temperature at various times during the lytic cycle. All the mutants showed an optimal response to the permissive pulse at a specific time after infection. The optimal responses of the mutants belonging to the same complementation group fell close together in the same time interval; the optimal responses of mutants contained in 20 different complementation groups were more or less uniformly scattered throughout the lytic cycle. Temperature sensitivity, therefore, seems to afford, at least in the case of phage a, an independent way of grouping the genes in an ordered sequence with respect to the steps they control. The successful synthesis, within the infected host cell, of each required macromolecular product at the proper time seems to be the necessary condition for the completion of the assembly process, which ultimately leads to the production of complete and active viral particles. Until now, only a gross distinction of the viral functions in two classes, early and late, has been proposed (6, 9, 10; H. Echols et al., personal

Genetic Map of Bacteriophage α

“…Table 1 gives a list of the 25 complementation groups, the total number of mutants which was assigned to each group, and the number of mutants produced in each cistron by the different mutagens. This classification differs slightly from the one already presented by Gaeta et al (20) on the basis of earlier complementation work performed on 69 of the mutants obtained with HA. One class, XX, has been deleted since later results showed that the previous assignment of a mutant to this class was the result of highly efficient intracistronic complementation.…”