A common procedure for DNA fingerprinting is restriction fragment length polymorphism (RFLP). In this method, DNA is extracted from a sample and cut into segments using special restriction enzymes. RFLP focuses on segments that contain sequences of repeated DNA bases, which vary widely from person to person. The segments are separated using a laboratory technique called electrophoresis, which sorts the fragments by length. The segments are radioactively tagged to produce a visual pattern known as an autoradiograph, or "DNA fingerprint," on X-ray film. A newer method known as short tandem repeats (STR) analyzes DNA segments for the number of repeats at 13 specific DNA sites. The chance of misidentification in this procedure is one in several billion. Yet another process, polymerase chain reaction, is used to produce multiple copies of segments from a very limited amount of DNA (as little as 50 molecules), enabling a DNA fingerprint to be made from a single hair. Once a sufficient sample has been produced, the pattern of the alleles (see genetics) from a limited number of genes is compared with the pattern from the reference sample. A nonmatch is conclusive, but the technique provides less certainty when a match occurs.
In criminal investigations, the DNA fingerprint of a suspect's blood or other body material is compared to that of the evidence from the crime scene to see how closely they match. The technique can also be used to establish paternity. First developed in the mid-1980s, DNA fingerprinting has been accepted in most courts in the United States, and has in several notable instances been used to exonerate or free persons convicted of crimes, but the Supreme Court has ruled (2009) that convicted criminals do not have a constitutional right to DNA testing. All states have established DNA fingerprint databases, and the Federal Bureau of Investigation has instituted a national DNA fingerprint database linking those of the states and including DNA collected in connection with federal offenses. DNA fingerprinting is generally regarded as a reliable forensic tool when properly done, but some scientists have called for wider sampling of human DNA to insure that the segments analyzed are indeed highly variable for all ethnic and racial groups. It is possible to create false genetic samples and use them to misdirect forensic investigators, but if those samples have been produced using gene amplification techniques they can be distinguished from normal DNA evidence.
The techniques used in DNA fingerprinting also have applications in paleontology, archaeology, various fields of biology, and medical diagnostics. It has, for example, been used to match the goatskin fragments of the Dead Sea Scrolls. In biological classification, it can help to show evolutionary change and relationships on the molecular level, and it has the advantage of being able to be used even when only very small samples, such as tiny pieces of preserved tissue from extinct animals, are available.
The Centre for DNA Fingerprinting and Diagnostics (CDFD) is an autonomous organization funded by the Department of Biotechnology (DBT), Ministry of Science and Technology, Government of India. CDFD receives funding also from other agencies on specific collaborative projects. In addition, DNA Fingerprinting and Diagnostics services provided by the centre support some of the activities. The Centre is recognized by the University of Hyderabad and Manipal Academy of Higher Education, Mangalore, for pursuing Ph.D. programme in Life Sciences.
The centre is equipped with world class state-of-the-art instrumentation and computing infrastructure to facilitate working in frontier areas of research in Life Sciences. There are presently around fifteen groups working on diverse research areas and the centre continues to attract leaders in related disciplines. CDFD is supported with a strong Bioinformatics facility and is the India node of the European Molecular Biology Network (EMBnet). CDFD is located in the fastest growing metropolitan city of Hyderabad, more popularly known as Cyberabad for its initiative and pioneering role in developing the state during the past few years in the area of information technology. CDFD started its operations in CCMB, a CSIR organisation, and is currently housed in an interim building in Nacharam. The administration set up is situated in a sprawling new building in Gandipet locality of Hyderabad outskirts.
The center is currently headed by Dr. J.Gowrishankar who is an elected fellow of the Indian National Academy of Sciences with Dr. E.A. Siddiq and Prof T.S. Ramasarma as the distinguished chairs.
Research at CDFD is focused largely on structural genetics, bacterial genetics and fungal pathogenetics, with special emphasis on bioinformatics and computational biology.