Feulgen stain

Proof by Feulgen and Ross Beck, or shortly the Feulgen reaction, is one of Joachim Wilhelm Robert Feulgen in 1924, co-developed histochemical method for the detection of deoxyribonucleic acid ( DNA). First, in the sample to be analyzed ( sample tissue sample of microorganisms), the DNA was hydrolyzed by acid, wherein the compounds of the base and the sugar molecule to be separated. It results in free aldehyde groups. The aldehydes arise with fuchsin acid ( Schiff's reagent ) a red-violet color. Detection of DNA residues is possible under the microscope.