Question

The colonies of recombinant bacteria appear white in contrast to blue colonies of nonrecombinant bacteria because of

• A. Inactivation of glycosidase enzyme in recombinant bacteria
• B. Non-recombinant bacteria containing $\beta$-galactosidase
• C. Insertional inactivation of alpha-galactosidase in nonrecombinant bacteria
• D. Insertional inactivation of $\alpha$-galactosidase in recombinant bacteria

Answer 1

Answer: (B)

Non-recombinant bacteria containing $\beta$-galactosidase

Answer 2

The colonies of recombinant bacteria appear white in contrast to blue colonies of nonrecombinant bacteria because of non-recombinant bacteria containing $\beta$-galactosidase.

In cloning experiments, blue-white screening is done to detect recombinant bacteria. α-complementation plays a major role evaluation of the recombinant nature of the bacteria.

• In normal cells, blue colonies are formed when β-galactosidase is active.
• In recombinant cells, α-complementation does not occur. No blue color is noted.
• It is due to the insertional inactivation of alpha-galactosidase in recombinant bacteria that the colonies of recombinant bacteria appear white in comparison to the blue colonies of non-recombinant bacteria.

Also Read:Bacterial Transformation