Basic dyes have a negative charge.

• A. True
• B. False
• C. Sometimes
• D. Always

Answer: (B)

In histology staining, basic dyes carry a positive charge because their molecules have protonated amine groups. This positive charge makes them cling to negatively charged cellular components, such as the DNA and RNA in nuclei, producing basophilic staining. Conversely, acidic dyes are negatively charged and target positively charged structures, yielding eosinophilic staining of cytoplasm and extracellular matrix. Therefore, basic dyes are not negatively charged; they are positively charged. A classic example is hematoxylin, a basic dye that stains nuclei, often paired with the acidic dye eosin to give the H&E contrast.