Restriction endonucleases used widely in RDT are obtained from

Options

A. Plasmids
B. Bacterial cells
C. Bacteriophages
D. All prokaryotic cells

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 essential tools in recombinant DNA technology (RDT) for manipulating genetic material.

2. **Source of Restriction Endonucleases**:
- These enzymes are primarily derived from bacteria and archaea. They serve as a defense mechanism for these organisms against invading viruses by cutting foreign DNA.

3. **Example of Restriction Endonucleases**:
- A well-known example of a restriction endonuclease is EcoRI, which is isolated from the bacterium *Escherichia coli* (E. coli). This enzyme recognizes a specific DNA sequence and cleaves the DNA at that site.

4. **Application in Recombinant DNA Technology**:
- In recombinant DNA technology, these enzymes are used to cut DNA into fragments, allowing scientists to insert or remove specific genes, facilitating genetic engineering processes.

5. **Conclusion**:
- Therefore, the correct answer to the question regarding the source of restriction endonucleases used in recombinant DNA technology is that they are obtained from bacteria and archaea.

### Final Answer
Restriction endonucleases used widely in recombinant DNA technology (RDT) are obtained from **bacteria and archaea**.

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