Susceptibility of a hybrid plasmid to excision of genetic material

A 5 Megadalton segment of DNA carrying a gene for kanamycin resistance from R447 b (a plasmid of group N of molecular weight 33 Megadaltons) has been inserted into Plac (a plasmid of the A--C complex of molecular weight 101 Megadaltons) to produce the recombinant plasmid Plac-R447 b (Coetzee, 1974). The recombinant plasmid is a typical member of the A--C complex except that entry of an N group plasmid into a Plac-R447 b+ recipient frequently leads to the loss of 5 Megadaltons of DNA (including the kanamycin resistance determinant) from the resident plasmid. In those transcipients from which kanamycin resistance is not eliminated, both plasmids are stably inherited.