Restriction endonuclease is used in

Options

A. tissue culture
B. genetic engineering
C. cell fractionation
D. regeneration of tissues

Answer

### Step-by-Step Solution:

1. **Definition of Restriction Endonuclease**:
- Restriction endonucleases, also known as restriction enzymes, are proteins that can cut DNA at specific sequences. They act as molecular scissors.

2. **Historical Context**:
- These enzymes were first discovered in 1963 in E. coli, where they were found to restrict the growth of bacteriophages (viruses that infect bacteria).

3. **Functionality**:
- The primary function of restriction endonucleases is to cut DNA into defined fragments. This ability to cleave DNA is crucial for various biotechnological applications.

4. **Applications in Genetic Engineering**:
- Restriction endonucleases are extensively used in genetic engineering. They allow scientists to manipulate DNA by cutting it at specific sites, enabling the isolation of genes or DNA segments.

5. **Other Functions**:
- Besides cutting DNA, restriction enzymes can also:
- Determine the order of genes within a DNA molecule.
- Analyze the chemical structures of genes and regulatory regions of DNA.
- Create new combinations of genes by facilitating the insertion of DNA fragments into vectors for cloning or other purposes.

6. **Conclusion**:
- In summary, restriction endonucleases are essential tools in molecular biology and genetic engineering, serving as a chemical knife to cut DNA, analyze genetic structures, and create new genetic combinations.