Sex factor in bacteria is

Options

A. chromosomal replicon
B. F-replicon
C. RNA
D. sex-pilus

Explanation

**Step-by-Step Solution:**

1. **Understanding Bacterial Reproduction**: Bacteria primarily reproduce asexually through binary fission. However, they can also exchange genetic material through processes that resemble sexual reproduction, which include transformation, transduction, and conjugation.

2. **Identifying the Sex Factor**: In the context of bacterial conjugation, the sex factor is a crucial element. It is a specific plasmid that enables the transfer of genetic material between bacterial cells.

3. **Types of Bacterial Cells**: Bacterial cells can be classified into two types based on the presence of the sex factor:
- **F-positive (F+) cells**: These cells contain the F-plasmid, which carries the sex factor.
- **F-negative (F-) cells**: These cells do not possess the F-plasmid and thus lack the sex factor.

4. **Role of the F-Plasmid**: The F-plasmid (or F-replicon) is responsible for the formation of a sex pilus, which is essential for the conjugation process. During conjugation, the F+ cell transfers genetic material to the F- cell through this pilus.

5. **Conclusion**: Given the options provided (chromosomal replicon, F-replicon, RNA, or the sex virus), the correct answer is the **F-replicon**, as it specifically refers to the plasmid that contains the sex factor necessary for conjugation in bacteria.

**Final Answer**: The sex factor in bacteria is the **F-replicon**.

---