A mixture of fragmented DNA was electrophoresed in an agarose gel. After staining the gel with ethidium bromide, no DNA bands were observed. What could be the reasons?

Explanation

To solve the problem of why no DNA bands were observed after electrophoresis of fragmented DNA in an agarose gel, we can break down the potential reasons step by step:

### Step-by-Step Solution:

1. **Contamination with Nucleases**:
- Nucleases are enzymes that degrade nucleic acids. If the DNA sample was contaminated with nucleases, they could have fragmented the DNA further, making it impossible to visualize any bands on the gel.

2. **Incorrect Electrophoresis Setup**:
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