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

Options

A. Insertional inactivation of alphagalactosidase 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

Explanation

### Step-by-Step Solution:

1. **Understanding the Context**: The question asks why recombinant bacteria appear white while non-recombinant bacteria appear blue. This involves understanding the role of a specific enzyme and a chromogenic substrate.

2. **Role of Alpha-Galactosidase**: Non-recombinant bacteria contain a plasmid that produces the enzyme alpha-galactosidase. This enzyme acts on a chromogenic substrate, leading to the production of a blue color in the colonies.

3. **Insertion of Foreign DNA**: When foreign DNA is inserted into the plasmid of the bacteria, it disrupts the normal function of the alpha-galactosidase enzyme. This process is known as insertional inactivation.

4. **Effect of Insertional Inactivation**: The insertion of foreign DNA into the plasmid inhibits the activity of the alpha-galactosidase enzyme. As a result, the chromogenic substrate is not processed, and the colonies do not produce the blue color.

5. **Resulting Colony Color**: Consequently, the colonies of recombinant bacteria, which have undergone this insertional inactivation, appear white because the chromogenic substrate remains unprocessed.

6. **Conclusion**: Therefore, the difference in color between recombinant (white) and non-recombinant (blue) bacteria is due to the insertional inactivation of the alpha-galactosidase enzyme caused by the insertion of foreign DNA into the plasmid.

### Final Answer:
The colonies of recombinant bacteria appear white in contrast to the blue colonies of non-recombinant bacteria because of the insertional inactivation of the alpha-galactosidase enzyme due to the insertion of foreign DNA into the plasmid.

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