Why would lac z gene be fused to coding sequence of chain A and B in plasmids of E.coli?

Options

A. Helps to form blue insulin which is more effective
B. Helps in selection of recombinant
C. Help in oral administration of insulin
D. All of these

Answer

To understand why the lacZ gene is fused to the coding sequences of chain A and B in plasmids of E. coli, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Introduction to Humulin Synthesis**:
- The lacZ gene is involved in the synthesis of humulin, which is a form of artificial insulin produced in E. coli through genetic engineering.

2. **Role of Genetic Engineering**:
- Genetic engineering techniques allow for the creation of recombinant DNA. This involves the insertion of specific genes into plasmids, which act as vectors to carry the desired genetic material.

3. **Plasmid Structure**:
- The plasmid contains the lacZ gene and the coding sequences for the insulin chains A and B. The lacZ gene is crucial for the identification of successful recombinants.

4. **Restriction Enzymes and Ligation**:
- Specific sites on the plasmid are cut using restriction endonucleases. The target gene (insulin chains A and B) is then ligated into the plasmid, resulting in recombinant DNA.

5. **Function of lacZ Gene**:
- The lacZ gene encodes for the enzyme β-galactosidase, which can break down lactose and produce a blue pigment when lactose is present. If the lacZ gene is intact, the E. coli will produce a blue color.

6. **Selection Marker**:
- When the insulin gene is successfully inserted into the lacZ gene, it disrupts the lacZ function. As a result, the bacteria will not produce the blue pigment, indicating that the recombinant DNA has been formed.

7. **Identifying Recombinants**:
- By using the lacZ gene as a selection marker, researchers can easily identify which E. coli cells have taken up the recombinant plasmid (those that do not produce blue color) versus those that have not (those that produce blue color).

8. **Conclusion**:
- Therefore, the fusion of the lacZ gene to the coding sequences of chains A and B serves as a crucial mechanism for selecting and identifying successful recombinant E. coli that can produce humulin.