The role of thymine dimer in the photo-inactivation of the bacteriophage T4υ 1

Abstract

Thymine dimer formation and ultraviolet inactivation at 260 mμ have been compared on one and the same population of the bacteriophage T4υ1. An average of 4·8 thymine dimer molecules are found in a phage per phage lethal hit. Thus a majority of thymine dimer molecules have no effect whatsoever upon plaque-forming ability. Comparison of formation rates yields the result that most thymine dimer molecules cannot be interstrand crosslinks. The rate of thymine dimerization is linear from the very lowest u.v. doses up to about 2000 ergs/mm2, after which it decreases. Thymine dimer is most probably formed between adjacent thymine molecules on the same strand of DNA.