When is a post-stain applied during the electrophoresis process?

A post-stain is applied after electrophoresis to visualize the bands of DNA, RNA, or proteins that have been separated during the process. Once the electrophoresis run is complete, the gel containing the separated samples is often immersed in a staining solution. This allows for the visualization of the bands on the gel, which is crucial for analysis. Stains such as ethidium bromide or Coomassie blue bind to the molecules and emit visible signals when exposed to UV light or other sources, indicating where the separated samples are located on the gel.

The other options do not accurately describe the timing of the application of a post-stain during the electrophoresis process.