DIFFERENTIAL MUTATION PRODUCTION BY THE DECAY OF INCORPORATED TRITIUM COMPOUNDS IN E. COLI.

We have studied the differential mutation production by the decay of incorporated tritium compounds in E. coli (WWU) using DNA-seeking precursors (H(3)-thymidine), RNA-seeking precursors (H(3)-uracil, H(3)-uridine), and protein-seeking precursors (H(3)-histidine, H(3)-proline). In particular we have determined the reversion frequency of an arginine locus. The reversion frequency is measured in units of revertants/surviving bacteria/H(3) decay, and has an average value of 1.84 x 10(-8) for H(3)-uridine and H(3)-uracil, 0.67 x 10(-8) for H(3)-thymidine, and 0.28 x 10(-8) for H(3)-proline and H(3)-histidine. Thus, the revertants are produced most effectively by H(3) decays when the label is introduced in the form of an RNA precursor. The macromolecular distribution of the label shows that 5 to 8 per cent of the H(3)-uridine or H(3)-uracil is incorporated into DNA.