True about Northern blot technique:

Ref: Ananthanarayan, Panther CJ. Textbook of Microbiology. 8th Edition. London: John Wiley & Sons; 2009. Pg. 69Explanation:Southern blotting: The highly sensitive technique for identifying DNA fragments by DNA-DNA hybridisation is called Southern blotting, after EM Southern who devised it. This technique has very wide applications in DNA analysis.Northern blotting: An analogous procedure for the analysis of RNA has been called northern blotting (as opposed to Southern blotting). Here the RNA mixture is separated by gel electrophoresis, blotted and identified using labelled DNA or RNA probes.Western blotting: A similar technique for the identification of proteins (antigens) is called immunoblotting (or, in conformity with other blotting techniques, western blotting). Here the protein antigen mixture is separated by SDS- PAGE (sodium dodecylsulfate-polyaciylamide gel electrophoresis), blotted on to nitrocellulose strips and identified by radiolabeled or enzyme- labeled antibodies as probes. E.g. Western blot test for detection of antibodies directed against different antigens of HIV