Southern Blot Technology

Southern blot technology is a method used for detection and quantification of a specific DNA sequence in DNA samples. Briefly, purified DNA from a biological sample (such as blood or tissue) is digested with restriction enzymes, and the resulting DNA fragments are separated by using an electric current to move them through a sieve-like gel or matrix, which allows smaller fragments to move faster than larger fragments. The DNA fragments are transferred out of the gel or matrix onto a solid membrane, which is then exposed to a DNA probe labeled with a radioactive, fluorescent, or chemical tag. The tag allows any DNA fragments containing complementary sequences with the DNA probe sequence to be visualized within the Southern blot. Southern blot may be used to study normal chromosomal or gene rearrangement, find similar sequences in other species or in the genome, identify the restriction fragment, identify insertions, rearrangements, deletions, and point mutations in genes, identify methylated sites in particular genes, etc.