Viral DNA after being converted from viral RNA by X, incorporates into host genome to undergo replication. What is 'X'?

Options

A. DNA polymerase
B. Restriction endonuclease
C. RNA polymerase
D. Reverse transcriptase

Explanation

To solve the question, we need to identify the enzyme 'X' that converts viral RNA into viral DNA, which then incorporates into the host genome for replication. Let's break down the process step by step:

### Step-by-Step Solution:

1. **Understanding the Process**: The question states that viral RNA is converted into viral DNA, which then integrates into the host genome. This is a key feature of certain viruses, particularly retroviruses.

2. **Identifying the Enzyme**: The conversion of RNA to DNA is not a common process in most organisms. However, retroviruses, such as HIV, utilize a specific enzyme to perform this conversion.

3. **Evaluating the Options**:
- **DNA Polymerase**: This enzyme is responsible for synthesizing DNA from a DNA template. It does not convert RNA to DNA, so it cannot be 'X'.
- **Restriction Endonuclease**: This enzyme cuts DNA at specific sequences and is used in recombinant DNA technology. It does not play a role in converting RNA to DNA, so it cannot be 'X'.
- **RNA Polymerase**: This enzyme synthesizes RNA from a DNA template. It is not involved in converting RNA to DNA, so it cannot be 'X'.
- **Reverse Transcriptase**: This enzyme specifically converts RNA into DNA. It is found in retroviruses and is responsible for the process described in the question.

4. **Conclusion**: Based on the evaluation of the options, the correct answer is that 'X' is **Reverse Transcriptase**. This enzyme allows the viral RNA to be converted into DNA, which can then integrate into the host genome for replication.

### Final Answer:
**X is Reverse Transcriptase.**

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