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

Options

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

Answer

To answer the question regarding why recombinant bacteria appear white while non-recombinant bacteria appear blue, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Context**:
- Recombinant bacteria are genetically modified organisms that have had DNA from another organism inserted into their genome. Non-recombinant bacteria are those that have not undergone this modification.

2. **Identifying the Color Difference**:
- The question states that recombinant bacteria appear white, while non-recombinant bacteria appear blue. This color difference is crucial to understanding the underlying biochemical processes.

3. **Role of Beta-Galactosidase**:
- Non-recombinant bacteria produce an enzyme called beta-galactosidase, which is responsible for breaking down lactose into glucose and galactose. When this enzyme is active, it can also cleave a substrate called X-gal, which produces a blue color.

4. **Insertional Inactivation in Recombinant Bacteria**:
- In recombinant bacteria, the insertion of foreign DNA (such as a gene of interest) into the beta-galactosidase gene leads to its inactivation. This process is known as "insertional inactivation." As a result, these bacteria cannot produce functional beta-galactosidase.

5. **Conclusion**:
- Since recombinant bacteria cannot produce beta-galactosidase due to its inactivation, they do not cleave X-gal and thus do not produce the blue color. Instead, they appear white.

6. **Final Answer**:
- The colonies of recombinant bacteria appear white in contrast to blue colonies of non-recombinant bacteria because of the insertional inactivation of beta-galactosidase in recombinant bacteria.