Restriction endonucleases are most widely used in recombinant DNA technology. They are obtained from

Options

A. Bacteriophase
B. Bacterial cells
C. Plasmids
D. All prokaryotic cells

Answer

### Step-by-Step Solution:

1. **Understanding Restriction Endonucleases**:
- Restriction endonucleases, also known as molecular scissors, are enzymes that cut double-stranded DNA at specific sequences known as restriction sites.

2. **Function of Restriction Endonucleases**:
- These enzymes play a crucial role in protecting bacteria from invading bacteriophages (viruses that infect bacteria) by cutting the viral DNA.

3. **Identifying the Source**:
- The question asks for the source of restriction endonucleases. The primary source of these enzymes is bacterial cells.

4. **Evaluating the Options**:
- **Option A: Bacteriophage** - Incorrect, as restriction endonucleases protect bacteria from bacteriophages.
- **Option B: Bacterial Cell** - Correct, as these enzymes are derived from bacterial cells.
- **Option C: Plasmids** - Incorrect, as plasmids are not the direct source of restriction endonucleases.
- **Option D: All Prokaryotic Cells** - Incorrect, since not all prokaryotic cells produce restriction endonucleases; specifically, they are derived from bacterial cells.

5. **Conclusion**:
- The correct answer is that restriction endonucleases are obtained from **bacterial cells**.