In a restriction digestion experiment, the sticky ends of vector rejoined forming a circular vector without insert. Which enzyme can be used to eliminate this possibility?

Options

A. DNA ligase
B. Alkaline phosphatase
C. DNA polymerase
D. RNA polymerase

Answer

To address the question regarding the elimination of the possibility of a circular vector forming without an insert during a restriction digestion experiment, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Problem**: In a restriction digestion experiment, the vector (which is a DNA molecule used to deliver genetic material into a cell) can sometimes rejoin itself without any insert DNA. This can lead to unwanted circular vectors that do not carry the desired genetic material.

2. **Identifying the Enzymes**: The question provides four options for enzymes that could potentially prevent this issue:
- DNA ligase
- Alkaline phosphatase
- DNA polymerase
- RNA polymerase

3. **Analyzing Each Option**:
- **RNA Polymerase**: This enzyme synthesizes RNA from a DNA template. It is not relevant to the ligation of DNA fragments.
- **DNA Polymerase**: This enzyme synthesizes new DNA strands from nucleotides. It is primarily involved in DNA replication and does not prevent the ligation of vectors.
- **DNA Ligase**: This enzyme is responsible for joining DNA fragments together by forming phosphodiester bonds. It would actually facilitate the rejoining of sticky ends, which is not what we want in this case.
- **Alkaline Phosphatase**: This enzyme removes phosphate groups from the ends of DNA. By dephosphorylating the 5' ends of the vector, it prevents the vector from being ligated back together, thus reducing the chance of circular vectors forming without an insert.

4. **Conclusion**: The enzyme that can be used to eliminate the possibility of the vector rejoining itself without an insert is **Alkaline Phosphatase**. This enzyme works by removing the 5' phosphate groups necessary for ligation, thereby preventing self-ligation of the vector.

### Final Answer:
**Alkaline Phosphatase** is the enzyme that can be used to eliminate the possibility of the sticky ends of the vector rejoining and forming a circular vector without an insert.

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