In recombinant DNA technique, the term vector refers to :

Options

A. plasmids that can transfer foreign DNA into a living cell
B. cosmids that can cut DNA at specific base sequence
C. plasmids that can join different DNA fragments
D. cosmids that can degrade harmful proteins

Answer

### Step-by-Step Text Solution:

1. **Understanding Recombinant DNA Technology**:
- Recombinant DNA technology involves combining DNA from different sources to create new genetic combinations. This is often used in biotechnology for various applications, such as producing insulin.

2. **Defining the Vector**:
- In the context of recombinant DNA technology, a vector is a DNA molecule that is used to carry foreign genetic material into another cell.

3. **Types of Vectors**:
- The most common vectors used are plasmids, which are small, circular pieces of DNA found in bacteria. Plasmids can replicate independently of the chromosomal DNA.

4. **Function of Vectors**:
- Vectors serve as vehicles to transfer the gene of interest (such as the gene for insulin) into a host organism (like E. coli). Once inside the host, the vector allows the gene to be expressed and produce the desired protein.

5. **Key Features of Vectors**:
- Vectors have specific features that make them suitable for gene transfer:
- **Origin of Replication**: This allows the vector to replicate independently within the host cell.
- **Selectable Markers**: These are genes that provide resistance to antibiotics, allowing for the identification of successfully transformed cells.
- **Restriction Sites**: Vectors contain specific sequences where restriction enzymes can cut the DNA, allowing the insertion of the gene of interest.

6. **Conclusion**:
- Therefore, in recombinant DNA techniques, the term "vector" specifically refers to plasmids or other DNA molecules that facilitate the transfer of genetic material into host cells, enabling the expression of foreign genes.