Which of the following can prove useful as a vector in both a prokaryote and eukaryote?

Options

A. YEp
B. Cosmid
C. Adenovirus
D. Retrovirus

Answer

To determine which vector can prove useful in both prokaryotes and eukaryotes, we need to analyze the options provided.

### Step-by-Step Solution:

1. **Understanding Vectors**:
- Vectors are tools used in recombinant DNA technology to transfer foreign genetic material into host cells. They play a crucial role in gene cloning and expression.

2. **Analyzing the Options**:
- **YEP (Yeast Episomal Plasmid)**:
- Developed by Beggs in 1978, YEP is designed to shuttle genes between E. coli (a prokaryote) and yeast (a eukaryote). This dual functionality makes it suitable for both types of organisms.
- **Cosmid**:
- A hybrid vector that combines features of plasmids and phage, primarily used for cloning DNA fragments. It is not typically used in eukaryotic systems.
- **Adenovirus**:
- This is a viral vector used mainly for gene therapy in eukaryotic cells, particularly for cancer treatment. It is not effective in prokaryotes.
- **Retrovirus**:
- Retroviruses are also primarily used as vectors in eukaryotic systems for gene delivery but do not function in prokaryotes.

3. **Conclusion**:
- Among the options, **YEP** is the only vector that can be used in both prokaryotic and eukaryotic systems, making it the correct answer.

### Final Answer:
The vector that can prove useful as a vector in both prokaryotes and eukaryotes is **YEP (Yeast Episomal Plasmid)**.