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An early method of detecting DNA polymorphisms still in use employs restriction endonucleases. These bacterial enzymes cut DNA at specific recognition sequences. Restriction enzymes cleave DNA into a characteristic set of fragments that can be separated by gel electrophoresis. Some polymorphisms alter recognition sequences, so that the enzyme no longer recognizes a site or recognizes a new site. This results in a new set of DNA fragments that can be compared to others to detect the differences. These differences are called restriction fragment length polymorphisms (RFLPs).

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Medicine EncyclopediaGenetics in Medicine - Part 3Polymorphisms - Coding And Noncoding Sequences, Identifying Polymorphisms, Rflps, Strs, Vntrs, And Snps, Uses Of Polymorphisms