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ZoologyNEET 2025Tools of recombinant DNA technology

Biotechnology: Principles and Processes

Blue and white selectable markers have been developed which differentiate recombinant colonies from non-recombinant colonies on the basis of their ability to produce colour in the presence of a chromogenic substrate. Given below are two statements about this method:

Statement I: The blue-coloured colonies have the DNA insert in the plasmid and they are identified as recombinant colonies.

Statement II: The colonies without blue colour have the DNA insert in the plasmid and are identified as recombinant colonies.

In the light of the above statements, choose the most appropriate answer from the options given below:

  1. A.Both Statement I and Statement II are correct
  2. B.Both Statement I and Statement II are incorrect
  3. C.Statement I is correct but Statement II is incorrect
  4. D.Statement I is incorrect but Statement II is correct✓

Solution

An insert in the lacZ gene destroys galactosidase, so recombinant colonies cannot turn the chromogenic substrate blue — recombinants are the white colonies. Statement I is wrong, Statement II is correct.

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