What is the purpose of staining DNA bands after electrophoresis?

The purpose of staining DNA bands after electrophoresis is to enhance their visibility for analysis. Once DNA fragments are separated on a gel, they are typically difficult to see because they are colorless and transparent. Stains such as ethidium bromide or SYBR Green bind to the DNA, allowing for the visualization of the DNA bands when exposed to UV light. This visibility is crucial for evaluating the size and quantity of the DNA fragments, as well as for determining the effectiveness of the electrophoresis process itself.

The other options do not align with the primary objective of staining. For instance, dissolving the gel or altering the charge of DNA would not assist in visualization, and while impurities might be present in samples, staining does not serve the purpose of purifying those samples. Thus, the enhancement of visibility through staining is essential for facilitating accurate analysis and interpretation of the experimental results.