Abstract
A number of well-characterized R plasmids (R1drd19.K1, R100-1, R46, R55-1, R64-11, R388 and R751) will mobilize an integrated amp gene from the chromosome of E. coli K-12. R391 will not act in this way. The process involves recombination and in each case the mobilizing plasmid acquires an additional piece of DNA of molecular weight 4 .times. 106. Acquisition of this DNA may impair the transfer properties of the recombinant plasmid in some cases. The process will occur in a recA background.