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Q.
In the process of insertional inactivation
Biotechnology : Principles and Processes
Solution:
Alternative selectable markers have been developed which differentiate recombinants from the non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substrate. In this, a recombinant $DNA$ is inserted within the coding sequence of an enzyme, $p$-galactosidase. This results into inactivation of the enzyme, which is referred to as insertional inactivation. The presence of a chromogenic substrate gives blue coloured colonies if the plasmid in the bacteria does not have an insert. Presence of insert results into insertional inactivation of the $P$-galactosidase and the colonies do not produce any colour, these are identified as recombinant colonies.