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

Options

A. DNA polymerase
B. DNA ligase
C. Alkaline phosphatase
D. Reverse transcriptase

Answer

To determine 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. **Understand the Concept of Self-Ligation**:
- In recombinant DNA technology, self-ligation refers to the unwanted joining of vector DNA molecules without the insertion of foreign DNA. This can lead to the formation of non-recombinant plasmids, which are not useful for cloning.

2. **Identify the Role of Enzymes**:
- Different enzymes play various roles in DNA manipulation. For instance:
- **DNA Polymerase**: Synthesizes new DNA strands.
- **DNA Ligase**: Joins DNA fragments together.
- **Alkaline Phosphatase**: Removes phosphate groups from the 5' ends of DNA.
- **Reverse Transcriptase**: Converts RNA into DNA.

3. **Focus on Alkaline Phosphatase**:
- Alkaline phosphatase is specifically known for removing the terminal 5-phosphate group from DNA. This is crucial because ligation (the joining of DNA fragments) requires a 5-phosphate group at the site of the nick.

4. **Conclusion**:
- By removing the 5-phosphate group, alkaline phosphatase prevents the vector DNA from self-ligating. Thus, it ensures that only the foreign DNA can be ligated into the vector, facilitating successful cloning.

5. **Final Answer**:
- The enzyme required to prevent unwanted self-ligation of vector DNA molecules in recombinant DNA technology is **Alkaline Phosphatase**.