Restriction Enzyme Digestion, Gel Electrophoresis, and Vacuum Blotting of DNA to Nylon Membranes

In 1975, Edwin Southern published a paper that revolutionized the molecular analysis of the genomes of organisms (
1
). This procedure enabled the detection of which fragment of
DNA
(out of the millions that compose the genome of a higher organism) contained sequences related to that of a radioactively labeled probe. It was thus possible to detect and genetically map restriction fragment length polymorphisms (RFLPs, reviewed in ref.
2
), to know how many copies of a gene were present in an organism, to map the restriction sites around a sequence of interest, and to check if a potentially transgenic organism had really integrated the input gene into its chromosome. Suitable selection of probes, so that they detected sequences that were highly polymorphic (
3
), enabled the identification of individuals from a population, and has led to the use of the method in forensic analysis. The identification of genes, or linked loci, affecting human disease, has also led to applications in clinical research.