Which vector can clone only a small fragment of DNA ?

Options

A. Bacterial artificial chromosome
B. Yeast artificial chromosome
C. Plasmid
D. Cosmid

Answer

To determine which vector can clone only a small fragment of DNA, we will analyze the cloning capacity of each of the given options:

1. **Bacterial Artificial Chromosome (BAC)**:
- BACs can clone DNA fragments ranging from 150 to 350 kilobase pairs (kbp). This is a relatively large size for cloning.

2. **Yeast Artificial Chromosome (YAC)**:
- YACs can clone larger fragments, typically from 100 to 1000 kbp. This is significantly larger than small DNA fragments.

3. **Plasmid**:
- Plasmids are capable of cloning smaller DNA fragments, typically in the range of 10 to 25 kbp. This makes plasmids suitable for cloning small fragments of DNA.

4. **Cosmid**:
- Cosmids can clone DNA fragments up to 45 kbp. While they can handle smaller fragments than BACs and YACs, they are still larger than what plasmids can clone.

From this analysis, we can conclude that the vector that can clone only a small fragment of DNA is the **plasmid**.

**Final Answer**: Plasmid

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