Other than DNA polymerase, which of the following enzymes involved in DNA synthesis ?

Options

A. Topoisomerase
B. Helicase
C. RNA primase
D. all of these.

Explanation

To solve the question regarding the enzymes involved in DNA synthesis other than DNA polymerase, we can break down the process of DNA replication and identify the key enzymes involved.

### Step-by-Step Solution:

1. **Understanding DNA Replication**:
- DNA replication is the process by which a parent DNA molecule is copied to produce two identical daughter DNA molecules. This process is crucial for cell division.

2. **Role of DNA Polymerase**:
- DNA polymerase is the primary enzyme responsible for elongating the DNA strand by adding nucleotides to the growing DNA chain. However, it cannot initiate the synthesis of a new strand.

3. **Initiation of DNA Synthesis**:
- The synthesis of DNA begins with the formation of a short RNA primer. This primer is synthesized by an enzyme called **RNA primase**. The RNA primer provides a starting point for DNA polymerase to begin adding DNA nucleotides.

4. **Unzipping the DNA Strands**:
- Before DNA polymerase can synthesize new DNA, the double helix structure of DNA must be unwound. This unwinding is performed by the enzyme **helicase**, which separates the two strands of DNA.

5. **Relieving Tension in DNA**:
- As the DNA strands are unwound, tension is created in the DNA molecule. The enzyme **topoisomerase** helps to relieve this tension by cutting the DNA, allowing it to unwind, and then rejoining it.

6. **Conclusion**:
- Therefore, aside from DNA polymerase, the enzymes involved in DNA synthesis include RNA primase, helicase, and topoisomerase. Hence, the correct answer to the question is that all of these enzymes play a role in DNA synthesis.

### Final Answer:
The correct answer is **option 4: all of these** (RNA primase, helicase, and topoisomerase).

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