Commercial kits are used by forensic pharmaceutical or biochemical laboratories to make human identification possible through the use of DNA profiling . Commercial kits make use of standardized combinations of short tandem repeat loci (sequences of genetic material, also known as STR) in specific types of polymerase chain reactions (also known as PCR technology), which results in human identifications made with an extremely high degree of certainty. By using commercial kits with PCR technology, DNA profiles can be generated from exceedingly small, very old, badly preserved, or partially decomposed samples.
The FBI is a world leader in the development of DNA typing technology and the CODIS system, used to identify the perpetrators of violent and serial crimes. In 1997, the FBI announced the isolation and selection of thirteen STR loci that would form the core of the CODIS database (national DNA database). The thirteen specific STR loci used by the FBI in the CODIS system are: D3S1358, vWA, FGA, TH01, D21S11, D8S1179, D18S51, TPOX, CSF1PO, D16S317, D5S818, and D7S820. The thirteenth STR locus is used for gender determination on the X and Y chromosomes.
Because the CODIS system is widely available, and the 13 FBI-recommended STR have been standardized, it is relatively simple to use the CODIS system with a commercial kit in order to make a highly accurate identification.
The advantages of using STR loci, PCR technology, and commercial kits are:
- The CODIS system is available worldwide.
- Using commercial kits, STR alleles can be very rapidly determined.
- STR alleles (one member of a pair or series of genes at a specific location on a specific chromosome ) are standardized and behave according to scientific principles which are well known and understood.
- The data are ideally suited to use within computerized database systems.
- Forensic laboratories all over the world are adding to the known DNA database.
- STR profiles require very minute samples for accurate determination of identification.
DNA samples can be obtained from nearly any human tissue, and are typically deposited at crime scenes in the form of blood , semen , tissue from the victim, hair follicles, and saliva . DNA samples are extracted from these (or other similar) items of evidence and compared to DNA extracted from reference samples from known individuals (either offenders or member's of the victim's biological family).
Commercial kits have done much to advance the speed and accuracy with which forensic scientists can use DNA technology to make human identifications.
see also Ancient cases and mysteries; Blood; Cold case; Cold hit; Decomposition; Electrophoresis.