DNA amplification is a powerful technique that has had an immense impact on scientific research in the past 2 decades. While polymerase chain reaction (PCR) is still the most popular method, alternative methods of DNA amplification are constantly being developed. In addition, the extraordinary versatility of PCR has led to its use in novel ways that have opened new avenues of research. These novel methods for DNA amplification and the versatility of PCR are highlighted in DNA Amplification: Current Technologies and Applications.
How are DNA fragments visualised during gel-electrophoresis? What is elution?

Explanation

### Step-by-Step Solution:

1. **Understanding Gel Electrophoresis**: Gel electrophoresis is a technique used to separate DNA fragments based on their size. When an electric current is applied, the negatively charged DNA moves towards the positive electrode.

2. **Staining the DNA**: After the DNA fragments have been separated in the gel, they need to be visualized. This is done by staining the gel with a fluorescent dye. A commonly used dye is Ethidium Bromide (EtBr), which intercalates between the bases of the DNA.

3. **Visualizing the DNA Fragments**: Once the gel is stained with the fluorescent dye, it is placed under a UV transilluminator. The UV light causes the dye to fluoresce, making the DNA bands visible. The intensity of the fluorescence corresponds to the amount of DNA present in each band.

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