Polymorphisms are inherited differences found among the individuals in a population. The term "polymorphism" is not synonymous with the term "mutation" in that mutations are variations found less frequently in a population or occur as nongermline changes usually in a tumor cell (somatic mutations). In the case of restriction fragment length polymorphisms (RFLP), DNA sequence differences alter RE recognition sites, manifested either as obliteration or creation of a restriction site. With obliteration of an RE site, the DNA of individuals with an RFLP exhibits a larger restriction fragment of DNA than those without the polymorphism. With creation of a new RE site, RE digestion results in two smaller fragments relative to the unaffected individual. In either case, the polymorphism is detectable by creation of a new restriction fragment pattern, that is, a restriction fragment length polymorphism. In PCR-RFLP, the PCR products are digested by one or a combination of REs and electrophoresed to detect polymorphisms or mutations which are seen as changes in the DNA fragment sizes reflected by changes in the band pattern on the gel.
Examples of Applications of PCR-RFLP Analysis
1. Detection of sickle-cell hemoglobin (HbS)
2. Detection of the Mnl I restriction enzyme polymorphism created by the Factor VLeiden mutation16
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