(1992) Forensic science laboratory using DNA fingerprinting. Overhead view of laboratory technicians checking DNA (deoxyribonucleic acid) autoradiograms. Labeling the DNA fragments in an electrophoresis gel with a radioactive marker chemical produces these. The gel is then placed on a 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.