Question

What are Southern blots used for?

Answer 1

The process of immobilization of sample nucleic acid in solid support is called blotting. For their specific detection the blotted nucleic acids are then used as targets in hybridization experiments. The establishment of non-covalent, sequence specific interaction between two or more complementary strands of nucleic acids into a single hybrid is called hybridization.

Complete answer:
Southern Blot: It is a hybridization technique for identification of particular size of DNA from a mixture of given samples. This technique was developed by Edward M. Southern in 1975.
Principle: Separation of DNA fragments by running them on gel electrophoresis and identification by labelled probe hybridization. During electrophoresis DNA fragments are separated on the basis of charge and size. After transferring separated DNA fragments on a nitrocellulose membrane, the desired DNA is detected using a specific complementary DNA probe.
A hybridization probe is short ssDNA, labelled with markers for their easy identification after hybridization.
Procedure:
Restriction digestion: By restriction endonuclease enzyme and amplification by PCR
Gel electrophoresis: SDS gel electrophoresis
Denaturation: Treating with HCl and NaOH
Blotting-
Baking and Blocking with (milk protein) in BSA
Hybridization using labelled probes
Visualization by autoradiogram
The Southern Blot technique is used for detection of specific DNA sequences in a given DNA sample.

Note:
An example of southern blotting technique is DNA fingerprinting. Used for criminal identification, victim identification and paternity testing. Used in RFLP (restriction fragment length polymorphism). Used for identifying mutations in the sequence of DNA, diagnosis of diseases caused by genetic defects.