RNA Blotting by Electrotransfer and RNA Detection

Northern blot, or RNA blot, is a widely used technique in molecular biology to detect and semi-quantify specific RNAs. The advantage of this method is its ability to simultaneously estimate the sizes and quantities of degraded or processed RNA products. Northern blotting involves the use of electrophoresis to separate RNA samples by size. These RNAs are then transferred and immobilized on a membrane, and the RNAs of interest are detected by hybridization using a sequence-specific labeled DNA probe. Agarose gels are typically used in routine procedures to allow for the separation and specific detection of high molecular weights (ranging from tRNA size to several kb RNAs). However, acrylamide gels are preferred when the separation of lower weight RNAs (ranging from 20 to 200 nucleotides) is required. Both approaches for RNA separation are presented here. The term "northern blot" originally referred to the capillary transfer of RNA from the electrophoresis gel to the blotting membrane. However, RNA transfer to the membrane by electrotransfer has also been proven to be a suitable and fast method for transferring RNAs from acrylamide and agarose gels to the membrane.