What is "ethidium bromide"

n. An intercalating agent commonly used as a nucleic acid stain, having the molecular formula C₂₁H₂₀BrN₃

Ethidium bromide is an intercalating agent commonly used as a fluorescent tag ( nucleic acid stain) in molecular biology laboratories for techniques such as agarose gel electrophoresis. It is commonly abbreviated as "EtBr", which is also an abbreviation for bromoethane. When exposed to ultraviolet light, it will fluoresce with an orange colour, intensifying almost 20-fold after binding to DNA. Under the name homidium, it has been commonly used since the 1950s in veterinary medicine to treat trypanosomiasis in cattle, a disease caused by trypanosomes. The high incidence of antibiotic resistance makes this treatment impractical in some areas, where the related isometamidium chloride is used instead. Ethidium bromide may be a mutagen, although this depends on the organism exposed and the circumstances of exposure.