In 1975, Edward M. Southern developed the technique of DNA separation and its hybridization. Therefore, in his honour this technique is known as ‘Southern blotting or Southern hybridization technique’.
A specific DNA fragment can be separated and identified in a heterologous population of DNA molecules on the basis of binding of DNA probe with its complementary DNA strand.
The genomic DNA is isolated from the clone and digested with restriction enzymes. The DNA fragments are separated by agarose gel electrophoresis.
Different DNA bands are formed on agarose gel which represents DNA fragments of varying sizes. These fragments are transferred from gel to nylon or nitrocellulose membrane. The process of DNA transfer is called ‘blotting’.
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A nitrocellulose membrane is put over the gel. Many layers of filter paper are placed over nitrocellulose membrane.
This assembly is put in a container having NaOH solution. NaOH denatures DNA and results in formation of single stranded DNA. DNA fragments are transferred from gel to membrane by capillary action.