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Restriction fragment length polymorphisms, or RFLPs, are differences among individuals in the lengths of DNA fragments cut by enzymes. Restriction enzymes are proteins that cut DNA at short, specific sequences called restriction sites. After a segment of DNA has been cut into pieces with restriction enzymes, researchers can examine the fragments using a laboratory method called gel electrophoresis, which separates DNA fragments according to their size. If two individuals have differences in their DNA sequences at particular restriction sites, then the restriction enzymes will cut their DNA into fragments of different lengths. There may also be differences in the number of DNA fragments observed among two or more individuals. RFLP analysis can be used as a form of genetic testing to observe whether an individual carries a mutant gene for a disease that runs in his or her family.

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