Which chemical is commonly used to stain DNA in gels?

• A. DAPI
• B. Acridine Orange
• C. Methylene Blue
• D. EtBr

Answer: (D)

DNA visualization in gels relies on dyes that bind to DNA and glow under UV or blue light. Ethidium bromide is the classic choice because it intercalates between DNA bases and, when excited by UV light, emits bright orange fluorescence. That strong signal makes distinct DNA bands in an agarose gel easy to see, even for many samples, and the dye is inexpensive and widely available, which is why it’s widely used in practice.

Other dyes exist but aren’t as well suited for gel visualization. DAPI is mainly used for fluorescence microscopy of fixed cells and nuclei, not typical gel visualization. Acridine orange can stain nucleic acids but often gives less consistent band clarity in gels. Methylene blue can stain DNA but is less sensitive and not the standard for routine gel work.