Restriction fragment length polymorphism

Method Usually, DNA from an individual organism is first amplified (multiple copies are made) by the polymerase chain reaction (PCR). It is then cut into restriction fragments at defined positions by restriction enzymes. The restriction fragments are then separated according to length by agarose gel electrophoresis. The resulting gel may be enhanced by Southern blotting.

Result The distance between the locations cut by restriction enzymes (the restriction sites) varies between individuals: so the length of the fragments varies, and the position of certain gel bands differs between individuals (thus polymorphism). This can be used to genetically tell individuals apart. It can also show the genetic relationship between individuals, because children inherit genetic elements from their parents. It is also used to deterimne the relationships among species.

See also: genetics -- retroposon