Which of the following is incorrect regarding gel electrophoresis?

Options

A. Agarose gel is used for separation of DNA fragments while polyacrylamide gels ate used for protein separation
B. Separated DNA fragments can be visualised with or without staining with ethidium bromide
C. The desired band of DNA containing gene of interest are extracted from gel by a process known as elution
D. DNA fragments separate according to their size through sieving effect of agarose gel

Answer

To determine which statement regarding gel electrophoresis is incorrect, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement 1**: "Agarose gel is used for separation of DNA fragments while polyacrylamide gel is used for separation of proteins."
- **Analysis**: This statement is correct. Agarose gel is indeed used for separating DNA fragments, and polyacrylamide gel is used for protein separation.

2. **Statement 2**: "Separated DNA fragments can be visualized with or without ethidium bromide."
- **Analysis**: This statement is incorrect. Ethidium bromide is a fluorescent dye that is necessary for visualizing DNA fragments under UV light. Without it, the DNA fragments cannot be seen as they are colorless.

3. **Statement 3**: "The desired band of DNA containing gene of interest is extracted from gel by the process known as elution."
- **Analysis**: This statement is correct. The process of elution involves extracting the desired DNA fragment from the gel after electrophoresis, typically using an elution buffer.

4. **Statement 4**: "DNA fragments separate according to their size through the sieving effect of agarose gel."
- **Analysis**: This statement is also correct. DNA fragments do separate based on size due to the sieving effect of the agarose gel, where smaller fragments move faster than larger ones.

### Conclusion:
After analyzing all the statements, the incorrect statement regarding gel electrophoresis is **Statement 2**: "Separated DNA fragments can be visualized with or without ethidium bromide."

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