ACrystal Violet
BFeulgen staining
CGiemsa staining
DMethylene blue
Answer:
B. Feulgen staining
Read Explanation:
The Feulgen stain is a histochemical technique that relies on a specific chemical reaction to identify DNA. The process involves two main steps:
Acid Hydrolysis: The tissue is first treated with a mild acid, such as hydrochloric acid (HCl). This step breaks the bond between the purine bases (adenine and guanine) and the deoxyribose sugar in the DNA backbone. This creates free aldehyde groups in the sugar.
Staining with Schiff's Reagent: The sample is then stained with Schiff's reagent, which is a colorless dye. The free aldehyde groups on the DNA react specifically with the Schiff's reagent, causing it to become a bright magenta or purple color.
Because RNA has a different sugar (ribose with an extra hydroxyl group), it is not hydrolyzed by the acid treatment and therefore does not react with Schiff's reagent. This makes the Feulgen stain highly specific for DNA. The intensity of the staining is directly proportional to the amount of DNA present, which makes this method useful for quantitative analysis of DNA content in cells.