Preferred fixatives for nucleic acids?

• A. Acetic alcohol and Carnoy solution
• B. Bouin's solution
• C. Osmium tetroxide
• D. Formalin

Answer: (A)

Targeting nucleic acid preservation means choosing fixatives that minimize cross-linking and keep DNA and RNA as intact as possible. Acetic acid in alcohol and Carnoy's solution do this by rapidly dehydrating and precipitating nucleic acids along with proteins, rather than forming extensive chemical cross-links. This helps downstream molecular work, such as DNA/RNA extraction, PCR, sequencing, and in situ hybridization, proceed with higher yield and quality.

Bouin's solution, while great for nuclear detail, contains picric acid and can complicate nucleic acid analysis due to potential interactions and over-fixation. Osmium tetroxide is specialized for ultrastructural lipid preservation and is not suited for nucleic acids. Formalin cross-links proteins and nucleic acids, making extraction and amplification more challenging, even though it’s widely used for routine histology.

So, for preserving nucleic acids effectively, acetic alcohol and Carnoy's solution are the preferred fixatives.