Assertion . Pili are tubular structures present in bacteria which help in conjugation
Reason. Formation of pili is controlled by `F^(+)` or fertility factor.

Options

A. both are true with reason and reason is correct explanation of assertion
B. both true but reason is but reason is not correct explanation of assertion
C. assertion true but reason is wrong
D. both are wrong

Answer

To solve the assertion and reason question, we will analyze both statements step by step.

### Step 1: Understand the Assertion
The assertion states that "Pili are tubular structures present in bacteria which help in conjugation."

- **Explanation**: Pili are indeed hair-like structures found on the surface of many bacteria. They are primarily made up of a protein called pilin. One of the main functions of pili is to facilitate conjugation, which is a form of sexual reproduction in bacteria where genetic material is transferred from one bacterium to another through direct contact.

### Step 2: Understand the Reason
The reason states that "Formation of pili is controlled by `F^(+)` or fertility factor."

- **Explanation**: The fertility factor (F factor) is a plasmid that carries genes necessary for the formation of sex pili. Bacteria that possess the F factor can form sex pili and are referred to as F+ (fertility positive) bacteria. However, not all pili are involved in conjugation, and the formation of all types of pili is not solely controlled by the F factor. Therefore, while the F factor is important for the formation of sex pili, it does not account for all pili in bacteria.

### Step 3: Analyze the Relationship Between Assertion and Reason
- The assertion is true: Pili are tubular structures that assist in conjugation.
- The reason is partially true but does not correctly explain the assertion because it implies that all pili formation is controlled by the F factor, which is not accurate.

### Conclusion
Based on the analysis:
- The assertion is true.
- The reason is true but does not provide a correct explanation for the assertion.

Thus, the correct answer is **Option B: Both are true, but the reason is not the correct explanation of the assertion.**

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