Southern blot

A Southern blot is a method in molecular biology of enhancing the result of an agarose gel electrophoresis by marking specific DNA sequences. The method is named after its inventor, the British biologist Edward Southern, and this caused other blot methods to be named similarly (for example, Western blot, Northern blot).

Method

1. The gel from the DNA electrophoresis is heated or treated with chemicals to cause the double-stranded DNA to separate into single strands.
2. The gel is then put onto a sheet of nitrocellulose membrane and baked. This moves the DNA from the gel to the membrane, and fixates it there.
3. The membrane is now treated with a hybridization probe - DNA with a specific sequence that pairs with the sequence you are looking for. The probe DNA is labelled so that it can be detected, usually by incorporating radioactivity or tagging the molecule with a fluorescent dye.

Result

The probe shows which of the fragments of the electrophoresis separation contains a certain DNA sequence.

See also : Restriction fragment length polymorphism, Genetic fingerprint, Northern blot, Western blot

External links

• an example course in the subject