Zoology · Biotechnology: Principles and Processes

NEET (UG) 2025 — Question 107

In the plasmid represented above, a foreign piece of DNA is inserted at the EcoRI site. Which of the following strategies will be chosen to select the recombinant colonies?

Option A:
Using a medium plate containing ampicillin and tetracycline.
Option B:
Blue color colonies will be selected
Option C:
White color colonies will be selected.
Correct
Option D:
Blue color colonies grown on ampicillin plates can be selected.

Answer: C

Step-by-step solution

The vector carries an ampicillin-resistance gene and the lacZ' gene; the EcoRI site lies within lacZ'. An intact lacZ' produces functional β-galactosidase, which hydrolyses X-gal and gives blue colonies. Inserting foreign DNA at the EcoRI site inactivates lacZ' (insertional inactivation). Recombinant cells cannot make β-galactosidase, so they do not hydrolyse X-gal and remain white. Nonrecombinant transformants appear blue on medium containing ampicillin, X-gal and IPTG. Therefore, recombinant colonies are selected as white colonies; answer C.

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Exam: NEET (UG) 2025
Paper: 2025 paper
Subject: Zoology
Chapter: Biotechnology: Principles and Processes
Topic: Cloning Vectors

Answer: C

Step-by-step solution

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