Restriction endonuclease enzyme are used in genetic engineering because they

Options

A. are proteolytic engymes which degrades harmful proteins
B. can cut DNA at variable sites
C. can cut DNA at specific base sequence
D. can jon DNA fragments

Answer

### Step-by-Step Solution:

1. **Understanding Restriction Endonucleases**:
- Restriction endonucleases, also known as restriction enzymes, are proteins that cut DNA at specific sequences. They act like molecular scissors, allowing scientists to manipulate DNA for various applications in genetic engineering.

2. **Functionality of Restriction Endonucleases**:
- These enzymes recognize specific nucleotide sequences in the DNA, known as palindromic sequences, and cut the DNA at these locations. This precise cutting is essential for genetic engineering, as it allows for the targeted manipulation of DNA.

3. **Analyzing the Options**:
- The question presents several options regarding the function of restriction endonucleases:
- Option 1: Proteolytic enzymes which degrade harmful proteins (Incorrect, as restriction endonucleases target nucleic acids, not proteins).
- Option 2: Can cut DNA at variable sites (Incorrect, as they cut at specific sites).
- Option 3: Can cut DNA at specific base sequences (Correct, as this is the primary function of restriction endonucleases).
- Option 4: Can join DNA fragments (Incorrect, as this is the function of DNA ligases, not restriction endonucleases).

4. **Conclusion**:
- The correct answer is that restriction endonucleases are used in genetic engineering because they can cut DNA at specific base sequences.