Which enzyme is required to prevent unwanted self-ligation of vector DNA molecules in recombinant DNA technology ?

Options

A. DNA polymerase
B. terminal transferase
C. alkaline phosphatase
D. reverse transcriptase

Answer

To answer the question regarding which enzyme is required to prevent unwanted self-ligation of vector DNA molecules in recombinant DNA technology, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Self-Ligation**:
- In recombinant DNA technology, self-ligation refers to the process where vector DNA molecules can join together without incorporating the desired foreign DNA. This is undesirable as it reduces the efficiency of cloning.

2. **Role of Enzymes in Cloning**:
- During the cloning process, specific enzymes are used to manipulate DNA. One of the key steps is to ensure that the vector DNA does not ligate to itself.

3. **Identifying the Enzyme**:
- The enzyme that is commonly used to prevent unwanted self-ligation is **alkaline phosphatase**.

4. **Mechanism of Action**:
- Alkaline phosphatase works by removing the 5' terminal phosphate group from the vector DNA.
- The presence of this phosphate group is crucial for ligation, as ligation requires a phosphate group at the 5' end of the DNA.

5. **Consequences of Removal**:
- By removing the 5' phosphate group, alkaline phosphatase ensures that the vector DNA cannot undergo self-ligation.
- This means that the vector is unable to ligate to itself and can only ligate with the foreign DNA that has compatible ends.

6. **Conclusion**:
- Therefore, the enzyme required to prevent unwanted self-ligation of vector DNA molecules in recombinant DNA technology is **alkaline phosphatase**.

### Final Answer:
The enzyme required to prevent unwanted self-ligation of vector DNA molecules in recombinant DNA technology is **alkaline phosphatase**.

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