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.