The hypervariable regions of DNA have Variable Number of Tandem repeats (VNTRs) of short nucleotide sequences which are specific for each individual (except for monozygotic twins). Variations also occur due to mutations, small deletions or insertions. Therefore, DNA cut by a particular endonuclease will have different lengths in different persons. This phenomenon is called Restriction Fragment Length Polymorphism. It is the basis of genetic (or DNA) fingerprinting and is useful in identifying individuals from their semen, blood or tissues or any other DNA sample and resolution of parent hood disputes.
Polymerase Chain Reaction (PCR) is also useful in genetic fingerprinting as it can amplify the DNA sample even if available in a very small amount.