What is ethidium bromide?

Ethidium bromide (3,8-Diamino-5-ethyl-6-phenylphenanthridinium) is a fluorescent dye that’s widely used to detect DNA in agarose gel electrophoresis experiments. It is available as a dark red, odorless, crystalline powder that’s moderately soluble in water.

Ethidium bromide (EtBr) is a flat, planar molecule that’s capable of intercalating or inserting itself between nitrogenous bases of a DNA molecule. On binding with double-stranded DNA, it experiences a roughly 20 - 25 fold increase in brightness and releases a red-orange fluorescence when excited by UV light. This makes it easier to visualize and tag DNA molecules in various molecular biology research procedures.

While it is an efficient tool for genomic research, the major drawback is that ethidium bromide is a potent mutagen.