Following agarose gel electrophoresis, DNA bands cannot be seen directly under visible light. What stain and illumination source are required to visualize them as bright orange bands?
Answer and explanation
Correct answer: C. Ethidium bromide (EtBr) staining visualized under ultraviolet (UV) light
- Step 1: Nucleic acids are colorless in visible light.
- Step 2: Ethidium bromide (EtBr) is a fluorescent dye that intercalates between stacked base pairs of double-stranded DNA.
- Step 3: When excited by ultraviolet (UV) radiation (), intercalated EtBr fluoresces brilliantly, revealing DNA as bright orange bands.
Answer
Ethidium bromide (EtBr) staining visualized under ultraviolet (UV) light.
Why not the others: Methylene blue requires visible white light and produces faint blue bands; Acetocarmine is a nuclear squash stain for chromosomes; Crystal violet is used in Gram staining of bacteria.
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