Restriction endonuclease

Options

A. Cuts the DNA molecule randomly
B. Cuts the DNA molecule at specific sites
C. Restricts the synthesis of DNA inside the nucleus
D. Synthesises DNA

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 are crucial tools in molecular biology and biotechnology.

2. **Function of Restriction Endonucleases**:
- These enzymes act as molecular scissors, recognizing specific sequences in the DNA known as restriction sites.

3. **Specificity of Cuts**:
- Unlike random cutting, restriction endonucleases cut DNA at precise locations. This specificity allows for targeted manipulation of DNA, which is essential in genetic engineering.

4. **Example of Restriction Sites**:
- A common example of a restriction site is the sequence "AAGGCC". The enzyme will recognize and cut the DNA at this specific sequence.

5. **Clarifying Misconceptions**:
- It is important to note that restriction endonucleases do not restrict the synthesis of DNA inside the nucleus, nor do they synthesize DNA. Their primary function is to cut DNA at specific sites.

6. **Conclusion**:
- The correct answer to the question about the function of restriction endonucleases is that they cut DNA at specific sites.