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Mini-STR Testing

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. Analysis of these compromised DNA samples often result in dropout of the larger STR loci from the sample, and only a partial DNA profile can be obtained. Partial DNA profiles generally do not provide the power of discrimination to include or exclude a potential contributor to the sample.

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. This technology dramatically increases the sensitivity of DNA detection and optimizes the opportunity to obtain a DNA profile from compromised samples.

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.

DDC utilizes the Applied Biosystems, Inc. MiniFiler™ kit, a 9-plex which includes the following loci: D13S317, D7S820, Amelogenin, D2S1338, D21S11, D16S539, D18S51, CSF1PO, and FGA. The MiniFiler™ kit is an adjunct kit to the Applied Biosystems autosomal STR kits to recover loci that are otherwise too fragmented or damaged for amplification.