TK Locus General Principles

The effects of BUdR and THMG selection media on TK-competent (TA +/+ or TK+I-) and TK-deficient (TK-i ) L5178Y cells are summarized in Table 5. (For reasons explained below, the TK locus is believed to be 

FIGURE 1. Biochemical pathways leading to the synthesis and utilization of thymidine monophosphate (TMP). TMP biosynthesis is effected both by the folate-dependent enzyme thymidylate synthetase (TS) and by thymidine kinase (TK). Using inhibitors of folate metabolism or lethal analogues of thymidine, the TS and TK pathways can be controlled to select for TK-competent or TK-deficient cells. For details, see text. 

Number of viable cells per flask Number of viable TK-i- cells per flask Number of colonies in BUDR d Number of colonies in THMG d 

Donald Clive, W, Gary Flamm, and James B. Patterson 

FIGURE 2. Effect of cell concentration on cloning efficiency of coplated TK cells in 

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