Identify the vector suitable for cloning long DNA fragments

Options

A. Phage vector
B. Bacterial plasmid
C. Yeast plasmid
D. Cosmids

Answer

### Step-by-Step Solution

1. **Understanding Vectors**: Vectors are DNA molecules used to transfer genetic material into a host cell. They can carry DNA fragments of varying sizes.

2. **Analyzing the Options**:
- **Phage Vector**: Capable of cloning DNA fragments of about 10 KB.
- **Bacterial Plasmid**: Can clone DNA fragments ranging from 10 KB to 20 KB.
- **Yeast Plasmid (YAC)**: Typically used as an expression vector and can carry around 500 KB, but it is not primarily a cloning vector.
- **Cosmids**: A hybrid vector that combines features of plasmids and phage, capable of carrying DNA fragments from 28 KB to 50 KB.

3. **Identifying the Suitable Vector**:
- Since the question asks for a vector suitable for cloning long DNA fragments, we need to focus on those that can accommodate larger sizes.
- The **Cosmid** is the only option that can carry DNA fragments up to 50 KB, making it the most suitable choice for cloning long DNA fragments.

4. **Conclusion**: The correct answer is **Cosmids** as they are designed to carry larger DNA fragments compared to the other options provided.