Question

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

• A. Non-recombinant bacteria contain betagalactosidase
• B. Insertional inactivation of alphagalactosidase in non-recombinant bacteria
• C. Insertional inactivation of alphagalactosidase in recombinant bacteria
• D. Inactivation of glycosidase enzyme in recombinant bacteria

Answer 1

Answer: (C)

Insertional inactivation of alphagalactosidase in recombinant bacteria

Insertional inactivation means inactivation of an enzyme by the presence of an insert (recombinant DNA). In the presence of a chromogenic substrate, active alpha-galactosidase enzyme yields blue coloured colonies (non recombinants). While insertional inactivation of alpha-galactosidase enzyme inactivates the enzyme resulting in white colour colonies (recombinants). Thus, it is due to insertional inactivation of alpha-galactosidase in recombinant bacteria that the colonies of recombinant bacteria appear white in contrast to the blue colonies of non-recombinant bacteria.

So, the correct answer is 'Insertional inactivation of alphagalactosidase in recombinant bacteria'.