Southern Blotting was invented by Professor Sir Edwin Mellor Southern.Southern Blotting is generally used to identify or in probing of DNA molecule with known or available molecular probes. Southern Blotting helps in isolating the sequence of our interest from the complex mixture.Steps involved in Southern Blotting :

1) DNA samples are digested by appropriate restriction endonucleases.

2) Digested DNA samples are run on agarose gel where they separate according to their size.

3) In case of double stranded DNA molecules are treated with alkaline (0.5M NaOH) solution to denature the double stranded DNA molecule to single strand, if the DNA fragments are more than 15kb then the DNA molecules are treated with 0.2M HCL for 15min. this takes out the purines(known as depurination) and make it easier to transfer the fragments to the nitrocellulose membrane/blotting membrane.

4) After this the gel is laid on the top of buffer saturated filter paper, with its two ends immersed in the buffer. Then the nitrocellulose membrane is placed on this setting, above the membrane upto 0.5kg weight is put(usually paper towel). The buffer solution moves up through the filter paper to the nitrocellulose membrane and eventually to paper towel, while moving up it carries DNA molecules from gel to nitrocellulose membrane, to which DNA get binds. This whole setting is left for few hours or overnight, after which paper towel are removed.