The rose-red staining shown in the image is which phenomenon?

• A. Metachromatic
• B. Basophilic
• C. Anisotropic
• D. Eosinophilic

Answer: (A)

Metachromasia is a staining phenomenon in which a basic dye changes color when bound to certain tissue components, producing a rose-red (or purple) appearance instead of the dye’s original blue. This occurs with substances like highly sulfated glycosaminoglycans in cartilage or mast cell granules, where the dye molecules interact to form complexes that absorb light differently. That color shift is what you’re seeing as rose-red.

Basophilic staining would keep the dye blue because it reflects binding to acidic components like nucleic acids, without a color shift. Eosinophilic staining would be pink/red from eosin binding to basic cytoplasmic components, not a metachromatic shift. Anisotropic refers to birefringence under polarized light, not a color change with standard dye staining.