Regional preference of insertion of Tn501 and Tn802 into RP1 and its derivatives.

The sites of insertion of Tn501 into RP1 and into derivatives of this plasmid that either lack the Tn801 (TnA) element or contain it in a different location have been determined. Similarly, the sites of insertion of Tn802 into a derivative of RP1 that lacks the Tn801 element and into recombinants of this plasmid with Tn501 were determined. 'Hot spots' for insertion were observed with both transposons; but it is clear that a particular DNA sequence is not sufficient to define a 'hot spot', since a particular region does contain many insertions when present in one plasmid but does not do so when part of another.