Short Tandem Repeats (STRs)

The human genome is full of repeated DNA sequences. These repeated sequences come in various sizes and are classified according to the length of the core repeat units, the number of contiguous repeat units, and/or the overall length of the repeat region. DNA regions with short repeat units (usually 2-6 bp in length) are called Short Tandem Repeats (STR). The number of repeats in STR markers can be highly variable among individuals, which make these STRs effective for human identification purposes. STRs with higher power of discrimination are chosen for human identification in forensic cases on a regular basis. It is used to identify victim, perpetrator, missing persons, and others. Beginning in 1996, the FBI Laboratory launched a nationwide forensic science effort to establish core STR loci for inclusion within the national database known as CODIS (Combined DNA Index System). The 13 CODIS loci are CSF1PO, FGA, TH01, TPOX, VWA, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51 and D21S11. These loci are nationally and internationally recognized as the standard for human identification. Our partner Forensic Laboratory routinely uses the 13 CODIS loci and has additional loci for an extensive and powerful STR testing battery if required.

Y-STR

Y- STRs are Short Tandem Repeats found on the male-specific Y Chromosome. The Y-STRs are polymorphic among unrelated males and are inherited through the paternal line with little change through generations. Y-STRs have been used by forensic laboratories to examine sexual assault evidence. In a sexual assault case. The male component will be easily detected, since only this part of DNA will be amplified. The Y-STR system is especially helpful when there are more than one assailant. The mixed pattern in the evidence can help to identify those males responsible for the assault. Y-STR is also used for non-sexual assault cases where mixed samples are collected from evidence. Performing Y-STR testing can help to identify all males who have contributed to the evidence.

Mitochondrial DNA (mtDNA)

Unlike nuclear DNA, which is passed from both mother and father to the offspring, mitochondrial DNA (mtDNA) is inherited only from the mother. Mitochondrial DNA is useful for forensic purposes because part of the mitochondrial genome is highly polymorphic, making it useful for human identification, and although mtDNA comprises less than 1% of the total DNA within a cell, its genes exist in high amounts. Because mtDNA is present in high copy number, it is very useful when analyzing degraded samples or samples that lack nuclear DNA. One example is hair, which is a common item of evidence, especially when there is little or no root present to test.

Mini-STR

In cases where DNA evidence is limited, either in quantity or quality, such as highly degraded samples that are exposed to environmental insults or inhibitors, standard STR testing is often inadequate. An innovative approach to solve this problem is now available with mini-STR, a testing system that exploits the ability of specially designed primers that preferentially target the larger STR loci. While standard STR primers target longer sequences that include the STR loci, mini-STR primers “zoom in” on the STR locus so that the resulting DNA product is smaller, thereby increasing the chances of successful amplification of the larger loci. Because of the ability to type very degraded samples, mini-STR technology can be expected to provide forensic scientists with another tool that captures genetic data from DNA samples of marginal and extremely low quality and quantity. Thus, many previously unsolvable human identity cases may be resolved with mini-STR technology.

Order a test onlinehereor call us at 877-436-8735 to receive the Specimen Collection Kit.