Retroviruses have

Options

A. only RNA as a genetic material
B. only DNA as genetic material
C. DNA and RNA as genetic material
D. genes on nucleoprotein complexes as genetic material.

Answer

**Step-by-Step Solution:**

1. **Understanding Retroviruses**: Retroviruses are a type of virus characterized by their genetic material, which is RNA. An example of a retrovirus is the Human Immunodeficiency Virus (HIV), which causes AIDS.

2. **Identifying Genetic Material**: The key feature of retroviruses is that their genetic material is solely RNA. This distinguishes them from other types of viruses that may have DNA as their genetic material.

3. **Enzyme Characteristics**: Retroviruses possess a unique enzyme known as reverse transcriptase. This enzyme allows the retrovirus to convert its RNA into DNA once it infects a host cell.

4. **Host Cell Interaction**: Upon entering a host cell, retroviruses utilize reverse transcriptase to change their RNA into DNA, which then integrates into the host's genome. This process is crucial for the replication of the virus.

5. **Evaluating Options**:
- The first option states that retroviruses have only RNA as genetic material, which is correct.
- The second option mentions only DNA as genetic material, which is incorrect since retroviruses do not have DNA as their genetic material.
- The third option suggests both DNA and RNA as genetic material, which is also incorrect because a virus can only have one type of genetic material at a time.
- The fourth option refers to genes and nucleoprotein complexes as genetic material, which is not applicable to retroviruses.

6. **Conclusion**: Based on the analysis of the options, the correct answer is that retroviruses have only RNA as their genetic material.

**Final Answer**: Retroviruses have only RNA as genetic material.

---