selection in the presence of thymidine , 5-bromodeoxyuridine , and trifluorothymidine was expected to produce clones deficient in thymidine kinase only , whereas those deficient in galactokinase were expected to be selected in the presence of 2-deoxy-d-galactose .
C0040077
thymidine
C0040987
trifluorothymidine