Question

Which of the following reagents stains DNA and is particularly used to show chromosomes during cell division?

• A. Borax Carmine
• B. Iodine
• C. Methylene blue
• D. Feulgen's stain

Answer 1

The correct option is D Feulgen's stain

The Feulgen technique selectively stains DNA, and under controlled conditions, can be used for the photometric determination of DNA content. The reaction consists of two steps. Fixed material is treated for 8-10 min with 1N HCl in a water bath or oven at 60°C. Afterwards, the material is immediately transferred into Schiff's reagent at room temperature (for at least 30 min or until the tissue stains deep purple). The material is then squashed in acetocarmine or aceto-orcein. It is recommended the the material be analyzed the same day, however, it can be kept at 4°C for a several days if necessary. Acid hydrolysis removes purine bases from the DNA, thereby unmasking free aldehyde groups. The aldehyde groups then react with Schiff's reagent, which results in the purple staining. RNA is not hydrolyzed by the HCl treatment and, thus, the reaction is DNA-specific.

So the correct option is 'feulgen stain'.