Q.Compare the various types of Blotting techniques.

Southern, Northern and Western blotting detect DNA, RNA and protein respectively, using the same gel-transfer-probe method.

Blotting techniques are used to detect and identify a specific biomolecule -- DNA, RNA, or protein -- within a complex sample, and all three share a similar general strategy: the molecules are first separated by size using gel electrophoresis, then transferred ('blotted') from the gel onto a solid membrane (nitrocellulose or nylon), and finally probed with a labelled molecule that specifically binds to the target of interest.

Southern blotting (named after its inventor, Edwin Southern) is used to detect specific DNA fragments or sequences. The DNA sample is first digested with restriction enzymes, the fragments separated by agarose gel electrophoresis, transferred onto a membrane, and then hybridised with a labelled, complementary DNA probe to identify the fragment(s) of interest. It is used in applications such as gene mapping and DNA fingerprinting.

Northern blotting is the analogous technique used to detect specific RNA molecules, most commonly mRNA, and is named by playful analogy with 'Southern'. The RNA sample is separated by gel electrophoresis, blotted onto a membrane, and probed with a labelled complementary probe. It is widely used to study gene expression, since it reveals whether and how much a particular mRNA transcript is present in a sample.

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