2025 Biotechnology: Principles and ProcessesSelectable Markers - Blue-White Screening Medium Question 12 of 132 in Biotechnology: Principles and Processes

In the represented plasmid, an alien piece of DNA is inserted at the EcoRI site within the β-Galactosidase gene. Which…

In the represented plasmid, an alien piece of DNA is inserted at the EcoRI site within the $\beta$-Galactosidase gene. Which of the following strategies will be chosen to select the recombinant colonies?
A Using ampicillin & tetracyclin containing medium plate.
B Blue color colonies will be selected.
C White color colonies will be selected.
D Blue color colonies grown on ampicillin plates can be selected.

The answer is C.

Solution

Insertional inactivation of the $\beta$-galactosidase gene results in white recombinant colonies on chromogenic substrate (X-gal).

Insertion of recombinant foreign DNA into the coding region of $\beta$-galactosidase causes insertional inactivation. Non-recombinants retain active enzyme producing blue colonies with X-gal, while recombinants cannot produce active enzyme and appear white.

Concept Insertional Inactivation

Biotechnology: Principles and Processes in past papers

132 questions from this chapter have appeared across 26 exam years.