Identification of recombinant plasmids by in situ colony hybridization.

After transformation, cells containing parental or recombinant plasmids are usually selected by taking advantage of an antibiotic resistance marker present on the vector plasmid. Cells containing recombinant plasmids can often be identified as containing recombinant plasmids by screening for the insertional inactivation of a second genetic marker on the plasmid. The presence of an insert can be verified, and its size determined, by restriction analysis of plasmid DNA isolated using a small-scale procedure such as that described in Chapter 27 .