Transformation is a procedure through which

Options

A. A piece of DNA is introduced in a host bacterium
B. A piece of DNA is introduced in a vector
C. A piece of DNA is introdued from protein
D. All

Answer

**Step-by-Step Solution:**

1. **Understanding Transformation**: Transformation is a process used in genetic engineering where a piece of DNA is taken up by a host organism. In the context of bacteria, this typically refers to the uptake of plasmid DNA.

2. **Identifying the Options**: The question provides four options:
- A) A piece of DNA is introduced in a host bacterium.
- B) A piece of DNA is introduced in a vector.
- C) A piece of DNA is introduced from protein.
- D) All of the above.

3. **Analyzing the Options**:
- **Option A**: This accurately describes transformation, as it involves introducing DNA into a host bacterium.
- **Option B**: This describes the initial step of genetic engineering where DNA is inserted into a vector (like a plasmid), but it does not describe transformation itself.
- **Option C**: This option is incorrect because transformation does not involve the introduction of DNA from proteins.
- **Option D**: This option cannot be correct because not all the statements are true.

4. **Conclusion**: Based on the analysis, the correct answer is **Option A**: A piece of DNA is introduced in a host bacterium.

**Final Answer**: Transformation is a procedure through which a piece of DNA is introduced in a host bacterium (Option A).

---