What is the reason for using restriction endonuclease as a tool for genetic engineering ?

Options

A. They can degrade harmful proteins.
B. They can cut DNA at specific base sequences.
C. They can cut DNA at variable sites.
D. They can join DNA fragments.

Answer

### Step-by-Step Solution:

1. **Understanding Genetic Engineering**:
- Genetic engineering involves techniques that alter the genetic material (DNA or RNA) of an organism. The goal is to modify the genetic makeup to introduce desired traits or characteristics.

2. **Role of Restriction Endonucleases**:
- Restriction endonucleases, also known as restriction enzymes, are crucial tools in genetic engineering. They are enzymes that can cut DNA at specific sequences.

3. **Specificity of Action**:
- These enzymes recognize specific base sequences in the DNA and make precise cuts. This specificity is essential for manipulating genes accurately.

4. **Applications in Genetic Engineering**:
- By cutting DNA at specific sites, restriction endonucleases allow scientists to isolate specific genes or DNA fragments. This can be used to insert, delete, or modify genes in a host organism.

5. **Joining DNA Fragments**:
- After cutting DNA, the resulting fragments can be joined together using another enzyme called ligase. This allows for the creation of recombinant DNA, which is a fundamental aspect of genetic engineering.

6. **Conclusion**:
- The primary reason for using restriction endonucleases in genetic engineering is their ability to cut DNA at specific sequences, enabling precise manipulation of genetic material.