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

1. Insertional inactivation of alpha-galactosidase in non-recombinant bacteria
2. Insertional inactivation of alpha-galactosidase in recombinant bacteria
3. Inactivation of glycosidase enzyme in recombinant bacteria
4. Non-recombinant bacteria containing beta-galactosidase

Correct answer: Insertional inactivation of alpha-galactosidase in recombinant bacteria

Solution

Recombinant bacteria carry the inserted DNA within the reporter gene, causing insertional inactivation of the enzyme needed to cleave the chromogenic substrate. As a result, they do not turn blue and instead appear white, while non-recombinant colonies retain enzyme activity and appear blue.

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