Which one of the following is used in genetic engineering ?

Options

A. RNA polymerase
B. DNA polymerase
C. Nuclease
D. Restriction endonuclease

Answer

### Step-by-Step Solution

1. **Understanding Genetic Engineering**:
- Genetic engineering, also known as genetic manipulation, is the process of altering the genetic makeup of an organism using recombinant DNA (rDNA) technology.

2. **Identifying the Options**:
- The options provided are:
- RNA polymerase
- DNA polymerase
- Nuclease
- Restriction endonuclease

3. **Analyzing Each Option**:
- **RNA Polymerase**:
- This enzyme is responsible for transcribing DNA into RNA. It is not directly involved in genetic engineering processes, making it an incorrect choice.
- **DNA Polymerase**:
- This enzyme synthesizes DNA molecules from nucleotides. While it plays a role in DNA replication and repair, it is not primarily used in genetic engineering, so it is also incorrect.
- **Nuclease**:
- Nucleases are enzymes that cleave the phosphodiester bonds between nucleotides in DNA or RNA. They are involved in DNA repair but are not specifically used for cutting DNA at specific sites in genetic engineering, making this option incorrect as well.
- **Restriction Endonuclease**:
- These are enzymes that cut DNA at specific recognition sequences known as restriction sites. They are essential tools in genetic engineering because they allow scientists to cut DNA in a controlled manner, making this the correct choice.

4. **Conclusion**:
- The correct answer to the question "Which one of the following is used in genetic engineering?" is **restriction endonuclease**.