Which can be used as vector for transfer of genes?
(a) BAC
(b) YAC
(c) Plasmid
(d) All the above

Options

A. BAC
B. YAC
C. Plasmid
D. All the above

Answer

To determine which can be used as a vector for the transfer of genes, let's analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Concept of Vectors**:
- A vector is a vehicle used to transfer genetic material into a host organism. It carries the gene of interest and facilitates its introduction into the target cells.

2. **Analyzing Option (a): BAC (Bacterial Artificial Chromosome)**:
- BACs are vectors derived from bacterial DNA. They can carry large fragments of DNA (up to 300 kb) and are commonly used in cloning and sequencing projects, including the Human Genome Project. Thus, BACs can be used as vectors for gene transfer.

3. **Analyzing Option (b): YAC (Yeast Artificial Chromosome)**:
- YACs are similar to BACs but are derived from yeast. They can also carry large DNA fragments (up to 1 Mb) and are used in genetic engineering and mapping of genomes. Therefore, YACs can also serve as vectors for gene transfer.

4. **Analyzing Option (c): Plasmid**:
- Plasmids are small, circular pieces of DNA found in bacteria. They are commonly used as vectors in genetic engineering because they can replicate independently of chromosomal DNA and can carry smaller DNA fragments (typically up to 15 kb). Thus, plasmids are also effective vectors for gene transfer.

5. **Conclusion**:
- Since all three options (BAC, YAC, and plasmid) can be used as vectors for the transfer of genes, the correct answer is:
- **(d) All the above**.

### Final Answer:
**(d) All the above**