Which stain allows DNA visualization under UV light?
DNA visualization requires a fluorophore excitable by UV transillumination. Ethidium bromide intercalates between base pairs and shows strong fluorescence enhancement upon binding, emitting orange light under UV. This allows detection of nanogram quantities of DNA within gel bands. Bromophenol blue and methyl blue are tracking dyes visible in white light, not fluorescent. Crystal violet stains proteins or bacterial cell walls and does not intercalate DNA. Therefore, ethidium bromide remains the prototypical UV-activated DNA stain, though safer alternatives like SYBR Green are now favored.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.