Restriction fragment length polymorphism (RFLP): a diagrammatic representation of sequential steps involved in DNA finger printing using RFLP.

Polymerase chain reaction (PCR) amplification of short tandem repeats (STRs)

Kary mullis in the year 1991 developed a technique to amplify a DNA. PCR generates the repeated copies of a specific area of the DNA fragment. These areas are the alleles and are specific sequences of base pairs. They are the target regions with variable length. On either side of the target regions there are "flanker" sequences which are non--variable regions. On chromosomes "flanker" occurs at same location for all individuals. Thousands of copies of a particular variable region are amplified by PCR which forms the basis of this detection. STR with a known repeat sequence is amplified and separated using gel-electrophoresis. The distance migrated by the STR is examined. For the amplification of STRs using PCR, a short synthetic DNA called primers are specially designed to attach to a highly conserved common non-variable region of DNA that flanks the variable region of the DNA. By comparing the STR sequence size amplified by PCR with the other known samples, will give the final result of the DNA Fingerprinting.

Applications of DNA Fingerprinting: 

1. In Forensics Science : DNA Fingerprinting and Forensics Forensic science can be defined as the intersection of law and science. The DNA profile of each individual is highly specific. The chances of two people having the exact DNA profile are 30,000 million to 1 (except for identical twins). Biological materials used for DNA profiling are: Blood, Hair, Saliva, Semen, Body tissue cells etc.

DNA isolated from the evidence sample can be compared through VNTR (Variable number of tandem repeats) prototype. It is useful in solving crimes like murder and rape. For example; the sex scandal of President Clinton with Monica Lewinsky, Double murders of O.J. Simpson in 1995. Colin Pitchfork was the first criminal caught based on DNA Fingerprinting evidence. He was arrested in 1986 for the rape and murder of two girls and was sentenced in 1988. O.J. Simpson was cleared of a double murder charge in 1994, which relied heavily on DNA evidence.

2. Paternity and Maternity Determination: A Person accedes to his or her VNTRs from his or her parents. Parent-child VNTR prototype analysis has been used to solve disputed cases. This information can also be used in inheritance cases, immigration cases. For Example: In 2002 Elizabeth Hurley used DNA profiling to prove that Steve Bing was the father of her child Damien.