Why is a stain required in gel electrophoresis?

In gel electrophoresis, a stain is required primarily to visualize the DNA. Since DNA is not inherently colored and cannot be seen by the naked eye, a staining agent binds to the DNA fragments, allowing them to become visible under specific illumination conditions, such as UV light. This visualization is crucial for analyzing the results of the electrophoresis, as it enables the researcher to see the distinct bands of DNA that have separated based on size.

While there may be other methods to enhance the gel quality or modify the separation process, the main functional purpose of staining in this context is directly linked to the visualization of the separated DNA fragments.