NEETZoologyBiotechnology - Principles and Processes
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In blue-white screening, the recombinant colonies do not produce any colour in the presence of a chromogenic substrate. Reason (R): The presence of a foreign DNA insert causes insertional inactivation of the -galactosidase gene, preventing the synthesis of the active enzyme. In the light of the abo
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
A. Both (A) and (R) are true and (R) is the correct explanation of (A)
Step-by-step solution
Assertion (A) is true because in blue-white screening, recombinant colonies appear white (colourless) when grown on a medium containing a chromogenic substrate. Reason (R) is also true and correctly explains Assertion (A). The insertion of a foreign DNA within the coding sequence of the -galactosidase gene results in insertional inactivation. Consequently, the active -galactosidase enzyme is not synthesized, and the chromogenic substrate is not cleaved to form a blue-coloured product. Non-recombinant colonies, whic