Which statement accurately describes DNA-staining capabilities?

• A. Feulgen only
• B. Methyl green-pyronin only
• C. Feulgen and methyl green-pyronin
• D. None of the above

Answer: (C)

DNA-staining methods can target DNA specifically or differentiate DNA from RNA. The Feulgen reaction is classic for DNA: after acid hydrolysis, the aldehyde groups on deoxyribose react with Schiff reagent to yield a magenta color that marks DNA specifically, with little to no staining of RNA. The methyl green-pyronin method is a two-color stain where methyl green binds DNA (giving green) and pyronin binds RNA (giving red), allowing simultaneous visualization and differentiation of the two nucleic acids. Because both methods produce a detectable stain for DNA, each provides DNA-staining capability, making the statement that both can stain DNA correct.