Here's why:
* Northern blotting uses an agarose gel, not a polyacrylamide gel. Polyacrylamide gels are used in SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis), which separates proteins by size. Formaldehyde is used in some SDS-PAGE protocols to maintain the integrity of protein structure.
* Northern blotting targets RNA, not proteins. RNA is separated by size using an agarose gel, not a polyacrylamide gel. Formaldehyde is not necessary to maintain RNA structure in this context.
Here's what is used in northern blotting gel preparation:
* Agarose: A polysaccharide that forms a gel matrix, separating RNA molecules by size.
* Buffer: Typically Tris-borate-EDTA (TBE) or Tris-acetate-EDTA (TAE) buffer, providing a conductive medium for electrophoresis.
* Formaldehyde (optional): Formaldehyde is *sometimes* added to the electrophoresis buffer during northern blotting, but this is not to prepare the gel itself. It is used to denature the RNA molecules, ensuring they migrate through the gel based on size alone, not structure.
In summary: Formaldehyde plays no role in northern blotting gel preparation. It's used in some protocols to denature RNA molecules during electrophoresis, but not in the gel itself.
