Different methods have been suggested to introduce alien DNA into host cells. Give and explain any three methods adopted for this purpose.

Explanation

To introduce alien DNA into host cells, several methods are employed. Here, we will discuss three commonly used methods: microinjection, electroporation, and the gene gun method.

### Step-by-Step Solution:

1. **Microinjection**:
- **Explanation**: Microinjection involves the direct injection of foreign DNA into the nucleus of a host cell. This is achieved using a fine glass needle (micro-needle) that is capable of penetrating the cell membrane without causing significant damage to the cell.
- **Process**: A micro-manipulator is used to position the needle accurately, and the foreign DNA is injected directly into the nucleus, allowing for immediate integration into the host's genetic material.

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