Question

Statement 1 : In insertional inactivation, blue colour produced by bacterial colonies indicates that the plasmid does not have an insert into the bacterial genome.
Statement 2: Presence of insert results into insertional inactivation of -galactosidase enzyme and the colonies do not produce any colour.

• A. Both statements 1 and 2 are correct
• B. Statement 1 is correct but statement 2 is incorrect
• C. Statement 1 is incorrect but statement 2 is correct
• D. Both statements 1 and 2 are incorrect

Answer 1

The correct option is A Both statements 1 and 2 are correct

Selectable markers have been developed which differentiate recombinants from 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 B-galactosidase. This results into an insertional inactivation. The presence of chromogenic substrate gives blue coloured colonies if the plasmid in bacteria does not have an insert. Presence of insert results into insertional inactivation of a^-galactosidase enzyme and the colonies do not produce any colour, these are identified as recombinant colonies.

So, the correct option is 'Option A' .