THYMIDINE-REQUIRING MUTANTS OF PHAGE T4

Abstract
Four mutants (td) of phage T4 have been isolated. They are deficient in their ability to grow in a thymine-requiring strain of E. coli without exogenous thymidine, but grow normally when thymidine is added. The mutants are all in the same cistron, which is responsible for the appearance of phage-controlled thymidylate synthetase activity. The td mutants map in a position far removed from a region controlling other functions that are also expressed early in phage development, showing that phage mutants affecting functions which are expressed at about the same time need not be arranged in contiguous regions of the map.