Which of the following reactions is the best choice to demonstrate only DNA?
A. Gallocyanin-chrome alum method.
B. Feulgen reaction.C. Solo chrome cyanine method.
D. Thioflavine S stain.
Ans. B. Feulgen reaction.
Gallocyanin-chrome
alum method will stain both DNA and RNA dark blue and, therefore, cannot provide a good estimate
on the amount of DNA in the cell. Thioflavine S stain can be used to
demonstrate amyloid deposition and must be visualized with a fluorescent
microscope. It cannot be used to estimate the amount of DNA in tissue sections.
Solo chrome cyanine method can be used to differentiate osteoid from newly
laid-down bone and older bone but does not stain DNA specifically. Feulgen
reaction stains DNA red-purple and the cytoplasm green and is a widely accepted
method to demonstrate DNA on histologic sections.
