Southern blotting is a laboratory technique used to detect and quantify a specific DNA sequence in DNA samples. It is named after its creator, British molecular biologist Edwin Southern, who first published it in 1975. The technique involves several steps, including:

1. DNA digestion: Purified DNA from a biological sample is digested with a restriction enzyme, which breaks the DNA into small fragments.
2. Gel electrophoresis: The DNA fragments are separated according to size using gel electrophoresis.
3. Blotting: The separated DNA fragments are transferred from the gel onto a blotting membrane.
4. Hybridization: A labeled DNA probe is added to the membrane, which hybridizes with any DNA fragments containing complementary sequences with the DNA probe sequence.
5. Detection: The labeled DNA fragments are visualized within the Southern blot.

Southern blotting is particularly useful for detecting large deletions in tumor genomes. It can also be used to analyze an organisms total DNA, also known as its genome, in order to identify a specific sequence of interest. The technique is labor-intensive but can reveal information about DNA identity, size, and abundance.