<prompt> Procedure used for analysis of RNANorthern blotSouthern blotWestern blotEastern blot  <response>: Ans. a Northern blot Ref. Harper biochemistry 27th ed., Fig. 39-5. Northern blot Similar to Southern blot, except that an RNA sample is electrophoresed. Useful for studying mRNA levels, which are reflective of gene expression. Southern DNA Northern RNA Western Protein.SOUTHERN BLOT Southern blotting is used to analyze whether genes have been deleted or rearranged. It is also used to detect restriction fragment length polymorphisms RFLPs. Genomic DNA is digested with restriction endonucleases and separated by gel electrophoresis. Individual fragments can then be transferred to a membrane and detected after hybridization with specific radioactive DNA probes.NORTHERN BLOT Northern blots are used to analyze patterns and levels of gene expression in different tissues. In a Northern blot, mRNA is separated on a gel and transferred to a membrane, and specific transcripts are detected using radiolabeled DNA as a probe. This technique has been largely supplanted by more sensitive and comprehensive methods such as reverse transcriptase RT-PCR and gene expression arrays on DNA chips. The Northern and Western blot transfer techniques are used to size and quantitate specific RNA and protein molecules, respectively. A fourth hybridization technique, the Southwestern blot, examines protein-DNA interactions. Proteins are separated by electrophoresis, renatured, and analyzed for an interaction by hybridization with a specific labeled DNA probe.Western blot Sample protein is separated via gel electrophoresis and transferred to a filter. Labeled antibody is used to bind to relevant protein. Confirmatory test for HIV after ELISA.Southwestern blot Identifies DNA-binding proteins e.g., transcription factors using labeled oligonucleotide probes. 