Transduction in bacteria is mediated by

Options

A. Plasmid vector
B. Phage vector
C. Cosmid
D. F-factor

Answer

### Step-by-Step Solution:

1. **Understanding Transduction**: Transduction is a method of genetic recombination in bacteria. It involves the transfer of DNA from one bacterium to another.

2. **Nature of Transduction**: This process does not require physical contact between the donor and recipient bacterial cells. Instead, it is mediated by a viral vector.

3. **Role of Viruses**: In transduction, foreign DNA is introduced into a bacterial cell by a virus. These viruses that specifically infect bacteria are known as bacteriophages (or phage vectors).

4. **Identifying the Correct Option**: Among the options provided:
- Plasmid vector: This is not involved in transduction.
- Phase vector: This refers to bacteriophages, which are indeed responsible for transduction.
- Cosmid: This is a type of vector used in cloning, not specifically in transduction.
- F vector: This is related to the transfer of plasmids via conjugation, not transduction.

5. **Conclusion**: The correct answer is that transduction in bacteria is mediated by a phase vector (bacteriophage).