DNA in an agarose gel is usually stained with 20-100 mg/ml
of ethidium bromide and visulized under a UV ligth.
A less toxic alternative is to stain DNA with methylene blue. Staining with
methylene blue takes longer and is less sensitive.
1. Pour 0.01-0.02% methylene blue solution into a staining tray.
2. Stain the agarose gel in the solution for 30 minutes.
3. Pour the methylene blue solution back to the stock bottle.
4. Destain with several changes of tap water.