Feulgen reaction is used to detect?
**Core Concept**
The Feulgen reaction is a histochemical staining technique used to detect DNA in tissues. It involves the hydrolysis of DNA with acid, followed by the Schiff reagent, which stains the resulting aldehyde groups. This technique is particularly useful for identifying and quantifying DNA in cells.
**Why the Correct Answer is Right**
The Feulgen reaction is specifically designed to detect DNA by taking advantage of the aldehyde groups formed during the acid hydrolysis of DNA. These aldehyde groups then react with the Schiff reagent, resulting in a characteristic purple stain. This staining pattern allows for the visualization and quantification of DNA in cells, making it an essential tool in cytology and histology.
**Why Each Wrong Option is Incorrect**
**Option A:** The Feulgen reaction is not used to detect RNA, which is typically stained using other techniques such as the methyl green pyronin stain.
**Option B:** The acid hydrolysis step in the Feulgen reaction is specific to DNA and would not effectively hydrolyze proteins.
**Option C:** The Schiff reagent is a specific stain for aldehyde groups, which are formed during the acid hydrolysis of DNA, not during the hydrolysis of other molecules.
**Clinical Pearl / High-Yield Fact**
The Feulgen reaction is a classic example of a histochemical staining technique that can be used to detect and quantify DNA in cells. It is often used in conjunction with other staining techniques to provide a comprehensive understanding of cell morphology and DNA content.
**Correct Answer: D. DNA.