Identifying clones
The plasmid vector contains another identifiable gene (e.g., a second drug resistance or an enzyme activity),
with the coding sequence of this gene containing the restriction site for insertion.
Insertion of the foreign DNA at this site interrupts the reading frame of the gene and result in insertional
mutagenesis.
In the example shown below, the b-galactosidase gene is inactivated. The substrate "X-gal" turns blue if the gene is intact, ie. makes active enzyme. White colonies in X-gal imply the presence of recombinant DNA in the plasmid.
|