Plasmid vector in DNA recombinant technology means

Options

A. A virus that transfers gene to bacteria
B. Extrachromosomal autonomously replicating circular DNA
C. Sticky end of DNA
D. Any fragment of DNA carrying desirable gene.

Answer

### Step-by-Step Solution:

1. **Understanding the Concept of Vectors**:
- In DNA recombinant technology, a vector is a carrier that is used to transfer foreign DNA or genes into host cells, which can be bacteria, plants, or animal cells.

2. **Identifying the Most Common Vector**:
- The most commonly used vector in this process is a plasmid.

3. **Defining Plasmids**:
- A plasmid is an extra-chromosomal, circular DNA molecule that is found in bacteria. It is capable of replicating independently of the chromosomal DNA.

4. **Functionality of Plasmids**:
- Plasmids can replicate on their own without interfering with the main genetic material of the host cell. This characteristic makes them ideal for use as vectors in recombinant DNA technology.

5. **Clarifying Other Terms**:
- Sticky ends are created when restriction endonucleases cut DNA. These ends can be used to attach new DNA fragments, but they do not define a plasmid vector.
- A fragment of DNA carrying a desirable gene is referred to as recombinant DNA, not a plasmid vector.
- Viruses can also transfer genes to bacteria, but they are not classified as plasmid vectors.

6. **Conclusion**:
- Therefore, a plasmid vector in DNA recombinant technology refers specifically to the circular DNA that can carry foreign genes into host cells for replication and expression.