Function of restriction endonuclease enzyme is

Options

A. Useful in genetic engineering
B. Protects the bacterial DNA against forein DNA
C. both a and b
D. Helpful in protein synthesis

Answer

### Step-by-Step Solution:

1. **Understanding Restriction Endonucleases**:
- Restriction endonucleases, also known as restriction enzymes, are proteins that recognize specific sequences of nucleotides in DNA and cut the DNA at or near these sites.

2. **Function in Bacteria**:
- These enzymes are primarily synthesized by bacteria as a defense mechanism. They help protect bacterial DNA from foreign DNA, such as that from viruses (bacteriophages). When foreign DNA is recognized, the restriction endonucleases cut it into fragments, thereby preventing it from integrating into the bacterial genome.

3. **Role in Genetic Engineering**:
- In genetic engineering, restriction endonucleases are invaluable tools. They are used to cut DNA at specific sites, allowing scientists to isolate a gene of interest from a larger DNA molecule. This gene can then be inserted into a vector (a DNA molecule used to transport foreign genetic material into another cell) for further study or manipulation.

4. **Evaluating the Options**:
- The options provided were:
- A) Useful in genetic engineering
- B) Protects the bacterial DNA against foreign DNA
- C) Both A and B
- D) Helpful in protein synthesis
- Based on the functions discussed, options A and B are correct. Therefore, the correct answer is C) Both A and B.

5. **Conclusion**:
- The function of restriction endonuclease enzymes includes both protecting bacterial DNA against foreign DNA and being useful in genetic engineering.