BACs and YACs are:

Options

A. Natural DNA obtained from bacteria and yeast
B. Useful vectors for eukaryotic gene transfer
C. Artifical DNA obtained from bacteria and yeast
D. Both (2) and (3).

Answer

**Step-by-Step Solution:**

1. **Understanding BACs and YACs**:
- BACs stands for Bacterial Artificial Chromosomes, and YACs stands for Yeast Artificial Chromosomes. Both are types of artificial chromosomes used in genetic engineering.

2. **Identifying the Nature of BACs and YACs**:
- They are not natural DNA; instead, they are artificially synthesized forms of DNA. This means they are created in a laboratory setting rather than occurring naturally.

3. **Function of BACs and YACs**:
- Both BACs and YACs serve as vectors. Vectors are DNA molecules that carry foreign genetic material into another cell. In this case, they are used for gene transfer in eukaryotic organisms.

4. **Evaluating the Options**:
- **Option 1**: "Natural DNA obtained from bacteria and yeast" - This is incorrect as BACs and YACs are artificial, not natural.
- **Option 2**: "Useful vectors for eukaryotic gene transfer" - This is correct as they are indeed used for this purpose.
- **Option 3**: "Artificial DNA obtained from bacteria and yeast" - This is also correct as BACs are derived from bacteria and YACs from yeast.

5. **Conclusion**:
- Since options 2 and 3 are correct, the best answer to the question is option 4: "Both 2 and 3".

**Final Answer**: BACs and YACs are both useful vectors for eukaryotic gene transfer and are artificial DNA obtained from bacteria and yeast.

---