Edwin Southern (born 1938), US biologist and deviser of the DNA analytical technique Southern blotting. This technique uses enzymes to fragment DNA (deoxyribonucleic acid), and the fragments are then separated in an electrophoresis gel. The separated fragments are then blotted" onto a nitrocellulose filter and marked with radioactive probes. The probes indicate the presence of specific genetic sequences (lengths of DNA that code for proteins). A sheet of photographic film is then laid over the filter. The radioactivity darkens the film, which reveals the position of genes in the DNA. This technique is widely used in genetic research. Photographed in 1983."