RNA retroviruses have an enzyme that

Options

A. Translates host DNA
B. Polymerises host DNA
C. Transcribes viral RNA to cDNA
D. Destroys host DNA

Answer

To solve the question "RNA retroviruses have an enzyme that," we will analyze the options and understand the role of retroviruses and the enzymes they possess.

### Step-by-Step Solution:

1. **Understanding Retroviruses**:
- Retroviruses are a type of virus that have RNA as their genetic material. This is important because it distinguishes them from other types of viruses that may have DNA as their genetic material.

2. **Identifying the Enzyme**:
- Retroviruses require an enzyme to convert their RNA into DNA. This is essential because the viral RNA must be integrated into the host's genome to replicate and produce new viral particles.

3. **Function of Reverse Transcriptase**:
- The specific enzyme that retroviruses use for this conversion is called reverse transcriptase. This enzyme synthesizes complementary DNA (cDNA) from the viral RNA.

4. **Analyzing the Options**:
- **Option 1: Translates host DNA** - This is incorrect because retroviruses do not translate host DNA; they need to convert their RNA to DNA.
- **Option 2: Polymerizes host DNA** - This is also incorrect; retroviruses do not polymerize host DNA.
- **Option 3: Transcribes viral RNA to cDNA** - This is correct, as reverse transcriptase transcribes the viral RNA into cDNA.
- **Option 4: Destroys the host DNA** - This option is incorrect; retroviruses do not destroy host DNA as their primary function.

5. **Conclusion**:
- The correct answer is that RNA retroviruses have an enzyme that "transcribes viral RNA to cDNA," which is facilitated by reverse transcriptase.

### Final Answer:
RNA retroviruses have an enzyme that transcribes viral RNA to cDNA.

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