Practice question

Ethidium bromide is a cationic phenanthridinium dye that intercalates between stacked base pairs of double-stranded DNA, with approximately one dye per 2.5 base pairs. Intercalation extends the helix and, upon UV excitation at 300 to 360 nm, emits orange fluorescence at 590 nm, enabling visualization of DNA bands within agarose or polyacrylamide gels. It does not participate in gel polymerization, does not denature DNA, nor catalyze reactions. While mutagenic and now often replaced by safer dyes, its mechanism remains classic DNA staining by intercalation.