Sites of insertion of TnA and TnM in RP1 and its derivatives.

The sites of insertion of TnM into the plasmid RP1, into derivatives of RP1 lacking TnA, and into derivatives in which the location of TnA within RP1 has been altered, were determined. Similarly, the sites of insertion of TnA into derivatives of RP1 from which TnA had been deleted, both with and without copies of TnM, have been examined. These studies show the presence in the plasmids of 'hot-spots' for TnA and TnM insertion. It is clear from the observations, however, that a particular DNA sequence in the recipient replicon is not sufficient to definite a 'hot-spot' since particular sequences sometimes do, and sometimes do not, contain many sites of insertion for a given transposon.