DNA fingerprinting. A laboratory technician making a visual check of a DNA autoradiograph (autorads). Autorads are produced by labelling the DNA fragments in an electrophoresis gel with a radioactive marker chemical. The gel is then placed on an piece of X- ray film, the radiation from the marker leaves a dark patch, representing each fragment, on the film after development. Comparison of autorads from two samples of DNA is the method by which a correlation may be made - so-called DNA fingerprinting. Photographed at Lifecodes Corp., a commercial laboratory in New York State, USA.