RADIATION-SENSITIVE MUTANTS OF T4D .I. T4Y - A NEW RADIATION-SENSITIVE MUTANT - EFFECT OF MUTATION ON RADIATION SURVIVAL, GROWTH AND RECOMBINATION

The isolation is described of a new radiation-sensitive mutant of T4, called y. T4y is an amber mutant in that its behaviour is only abnormal when growing on bacterial strains which do not possess an amber suppressor. During growth in such strains y has the following properties, compared to wild-type T4: (1) Twice the sensitivity to irradiation with UV light; (2) 30% more sensitivity to irradiation with γ-rays; (3) Normal photoreactivation; (4) Slightly reduced multiplicity reactivation; (5) Slower rate of intracellular phage development, and a burst size reduced by about one half; (6) In crosses homozygous for y the recombination frequency between two standard markers is reduced by about one half. In all these characteristics the behaviour of y has been experimentally compared with that of the two previously isolated radiation-sensitive mutants of T4, v and x. The comparison suggests that y functions in a similar manner to x, and differently from v. © 1969.