The enzyme that cuts DNA is :

Options

A. DNA -polymerase
B. DNA-lyase
C. DNA- ligase
D. Restriction endonuclease

Answer

To determine the enzyme that cuts DNA, we need to analyze the functions of the given options: DNA polymerase, DNA lyase, DNA ligase, and restriction endonuclease.

### Step-by-Step Solution:

1. **Identify the function of DNA polymerase**:
- DNA polymerase is responsible for synthesizing DNA. It catalyzes the formation of new DNA strands during DNA replication. Therefore, it does not cut DNA.
- **Conclusion**: DNA polymerase does not cut DNA.

2. **Examine the function of DNA lyase**:
- DNA lyase is involved in DNA repair processes. Specifically, it plays a role in the base excision repair pathway, which is crucial for fixing damaged DNA. It does not cut DNA but rather helps in repairing it.
- **Conclusion**: DNA lyase does not cut DNA.

3. **Evaluate the function of DNA ligase**:
- DNA ligase is an enzyme that joins together DNA fragments. It is essential for sealing nicks in the DNA backbone during replication and repair processes. Thus, it also does not cut DNA.
- **Conclusion**: DNA ligase does not cut DNA.

4. **Analyze the function of restriction endonucleases**:
- Restriction endonucleases, also known as restriction enzymes, are specialized enzymes that cut DNA at specific recognition sites within the DNA molecule. They are crucial for molecular cloning and genetic engineering as they create fragments of DNA.
- **Conclusion**: Restriction endonucleases are the enzymes that cut DNA.

### Final Answer:
The enzyme that cuts DNA is **restriction endonuclease**.

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