Which of the following statements is not true for retroviruses

Options

A. DNA is not present at any stage in the life cycle of retroviruses
B. Retroviruses carry gene for RNA - dependent DNA polymerase
C. The genetic material in mature retroviruses is RNA
D. Retroviruses are causative agents for certain kinds of cancer in man

Answer

To solve the question, we need to analyze each statement regarding retroviruses and determine which one is not true.

### Step-by-Step Solution:

1. **Understanding Retroviruses**:
Retroviruses are a type of virus that primarily contain single-stranded RNA as their genetic material. They also possess an enzyme called reverse transcriptase that allows them to convert their RNA into DNA once they infect a host cell.

2. **Analyzing Each Statement**:
- **Statement 1**: "DNA is not present at any stage in the life cycle of retroviruses."
- This statement is **not true**. Although retroviruses have RNA as their genetic material, they do produce DNA during their life cycle through the action of reverse transcriptase. Therefore, DNA is present at the stage when the RNA is reverse transcribed into DNA.

- **Statement 2**: "Retroviruses carry gene for RNA dependent DNA polymerase."
- This statement is **true**. Retroviruses do carry the gene for reverse transcriptase, which is an RNA-dependent DNA polymerase. This enzyme synthesizes DNA from an RNA template.

- **Statement 3**: "Genetic material in mature retroviruses is RNA."
- This statement is **true**. The mature form of retroviruses contains RNA as its genetic material.

- **Statement 4**: "Retroviruses are causative agents for certain kinds of cancer in men."
- This statement is **true**. Some retroviruses, like HTLV-1, are known to be oncogenic and can lead to cancers such as adult T-cell leukemia.

3. **Conclusion**:
The statement that is **not true** for retroviruses is **Statement 1**: "DNA is not present at any stage in the life cycle of retroviruses."

### Final Answer:
The statement that is not true for retroviruses is: **"DNA is not present at any stage in the life cycle of retroviruses."**

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