text: Before the "fingerprint" analysis, the DNA must be sampled and stored properly. Even blood or semen that has soaked into a rug or dried in the sunlight can be a source for sample cells. An analysis can be done from as few as 100 cells but requires several steps:\n\n\nScientists extract DNA from the cells.\n\nRestriction enzymes cut the DNA into pieces of various sizes.\n\nGel electrophoresis separates pieces by size.\n\nSeparated pieces are transferred to a nylon membrane, and some sequences are labeled with a radioactive substance called a probe.\n\nX-ray film is exposed by the radioactive emissions of only the labeled sequences. The developed film, called an autorad, shows the familiar track pattern of a DNA profile. \n\n\nCheck OJ Simson case, DNA Fingerprinting was used