text: where can i find primary sources of dna fingerprinting?   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:   scientists extract dna from the cells.  restriction enzymes cut the dna into pieces of various sizes.  gel electrophoresis separates pieces by size.  separated pieces are transferred to a nylon membrane, and some sequences are labeled with a radioactive substance called a probe.  x-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.    check oj simson case, dna fingerprinting was used