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

Options

A. lnsertional inactivation of alphagalac- tosidase in recombinant bacteria
B. Inactivation of glycosidase enzyme in recombinant bacteria
C. Non-recombinant bacteria containing beta- galactosidase
D. insertional inactivation of alphagalac- tosidase in non-recombinant bacteria

Answer

3

Explanation

In insertional inactivation a recombinant DNA is inserted within the coding sequence of enzyme J3 - galactosidase. If the plasmid in the bacteriadoes not have the insert (i.e., non - recombinants) then the chromogenic substrate gives blue coloured colonies. Presence of the insert (i.e., recombinants) leads to inactivation of the J3-galactosidase enzyme thus the colonies do not produce any colour.
Option ( l) is wrong, it should be `beta` galactosidase
Option (2) is wrong, it should be galactosidase instead of glycosidase
Option (3) is correct, as the non- recombinants have the `beta` galactosidase enzymes intact.
Option ( 4) is wrong it should be "Insertional inactivation of B galactosidase of recombinant bacteria".