Genetic evidence that Tn10 transposes by a nonreplicative mechanism

We present genetic evidence that the tetracycline resistance element Tn10 transposes by a nonreplicative mechanism. Heteroduplex Tn10 elements containing three single base pair mismatches were constructed on lambda phage genomes and allowed to transpose from lambda into the bacterial chromosome. Analysis of TetR colonies resulting from such transpositions suggests that information from both strands of the transposing Tn10 element is transmitted faithfully to its transposition product. The simplest interpretation of these results is that the transposing element is excised from the donor molecule and inserted into the target molecule without being replicated. A mismatch 70 base pairs from one end of the transposon is preserved, suggesting that there is little or no replication, even at the termini of the element, during transposition in vivo.