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Topic: Tools: restriction enzymes, vectors, host· Biotechnology and Its Applications

The 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 presence of a chromogenic substrate.Given below are two statements abo…

The 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 presence of a chromogenic substrate.

Given below are two statements about this method:

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

Statement II : The colonies without blue colour have 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. Both Statement I and Statement II are correct

2. Both Statement I and Statement II are incorrect

3. Statement I is correct but Statement II is incorrect

4. Statement I is incorrect but Statement II is correct

1 answer

Best answer

Answer: 4. Statement I is incorrect but Statement II is correct

Key idea: Insertional inactivation of the lacZ gene (β-galactosidase).

In a recombinant plasmid, the insert disrupts lacZ, so no enzyme forms and the colony stays white. Non-recombinants make a functional enzyme and give a blue colour. So Statement I is wrong and Statement II is right. Option 4.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report
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