Which of these restriction endonucleases are used in rDNA technology ?

Options

A. Type I
B. Type II
C. Type III
D. All of these

Answer

To answer the question regarding which restriction endonucleases are used in recombinant DNA (rDNA) technology, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Restriction Endonucleases**:
- Restriction endonucleases are enzymes that cut DNA at specific sequences. They are primarily found in bacteria and serve as a defense mechanism against viruses.

2. **Types of Restriction Endonucleases**:
- There are three main types of restriction endonucleases: Type 1, Type 2, and Type 3.
- **Type 1**: These enzymes have both methylation and restriction activities in a single enzyme, and they cut DNA at random positions.
- **Type 2**: These enzymes are the most commonly used in rDNA technology. They have separate activities for restriction and methylation, allowing them to cut DNA at specific sequences.
- **Type 3**: These enzymes also have separate activities but cut DNA outside of their recognition sites, making them less useful for precise genetic engineering.

3. **Identifying the Useful Type**:
- In recombinant DNA technology, the goal is to cut DNA at specific locations to insert or modify genes. Type 2 restriction endonucleases are preferred because they recognize specific sequences and cut at those sites, making them ideal for genetic engineering applications.

4. **Conclusion**:
- Therefore, the restriction endonucleases that are used in rDNA technology are primarily **Type 2 restriction endonucleases**.

### Final Answer:
Type 2 restriction endonucleases are used in recombinant DNA technology.

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