Figure 22.5: Insertional Inactivation of cI gene to screen recombinant clone.

Antibiotic sensitivity- Vector carries a functional selection marker such as antibiotic resistance gene to be use to select the clone. The antibiotic resistance gene product has multiple mechanism to provide resistance in host cell (Table 22.1). In this approach, a circular plasmid containing antibiotic resistance can be able to replicate into the host cell plated on a antibiotic containing media. In the cloning of a fragment into this plasmid, the plasmid is cut with restriction enzymes and a fragment in ligated to give circular plasmid with insert. The transformation of both DNA species; cut plasmid and circularized clone into the host and plated onto the antibiotic containing solid media. Only circularized clone will give colonies where as cut plasmid will not grow as it has lost antibiotic resistance gene. This approach is schematically depicted in Figure 22.6.