Incorporation of 5-substituted uracil derivatives into nucleic acids. The isolation and gamma-radiation-sensitivity of bacteriophage T3 containing the thymine analogue 5-vinyluracil.

Bacteriophage T3 was produced in a form that contained 32% of its normal DNA thymine residues replaced with 5-vinyluracil residues by infecting a thymine-requiring strain of Escherichia coli with phage T3 in a medium containing 5-vinyluracil. When 2'-deoxy-5-vinyluridine was added to the medium instead, no incorporation was observed into the phage DNA, and the presence of the deoxyribonucleoside severely decreased the number of viable phage particles produced. The analogue-containing phage, although initially viable, rapidly lost viability when stored, but it was no more sensitive than was normal phage T3 to the effect of gamma-radiation.