Question

In the process of insertional inactivation ________________.

• A. A recombinant DNA is inserted within the coding sequence of enzyme -galactosidase, resulting in inactivation of the enzyme
• B. A recombinant DNA is inserted within the coding sequence of proteins involved in the replication of the plasmid
• C. A recombinant DNA is inserted within the recognition site for EcoRI
• D. None of the above

Answer 1

The correct option is A A recombinant DNA is inserted within the coding sequence of enzyme -galactosidase, resulting in inactivation of the enzyme

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, 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 -galactosidase gene and the colonies do not produce any colour, these are identified as recombinant colonies.

So, the correct answer is 'A recombinant DNA is inserted within the coding sequence of enzyme -galactosidase, resulting in inactivation of the enzyme'