Which of the following techniques can be used to introduce foreign DNA into cell?

Options

A. Using disarmed pathogen
B. Microinjection
C. Gene gun
D. All of these

Answer

To answer the question regarding which techniques can be used to introduce foreign DNA into a cell, we will analyze each of the options provided:

### Step-by-Step Solution:

1. **Understanding Genetic Engineering**:
- Genetic engineering involves introducing foreign DNA into a host cell to alter its genetic material. This is done to express desirable traits or eliminate undesirable ones.

2. **Option 1: Using Disarmed Pathogen**:
- Disarmed pathogens can be used as vectors to introduce foreign DNA. They are modified to be non-virulent, meaning they do not cause disease in the host. This method is effective for delivering genetic material without the risk of pathogenic effects.

3. **Option 2: Microinjection**:
- Microinjection is a technique where a fine needle (microneedle) is used to inject foreign DNA directly into the nucleus of a host cell. This method allows for precise delivery of genetic material into the target cell.

4. **Option 3: Gene Gun**:
- The gene gun technique involves bombarding cells with microprojectiles made of gold or tungsten that are coated with foreign DNA. These projectiles penetrate the cell membrane and deliver the DNA into the cells at high velocity.

5. **Conclusion**:
- All three methods (disarmed pathogens, microinjection, and gene gun) are valid techniques for introducing foreign DNA into cells. Therefore, the correct answer is **Option 4: All of these**.

### Final Answer:
**All of these techniques can be used to introduce foreign DNA into a cell.**

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