Challenging DNA samples solved with MiniSTR analysis. Brief overview

Abstract

The recovery of genetic information from highly degraded or minute amount of biological samples needs special approaches together with conventional STR multiplex assays. In this respect, the "mini-STR" technology is considered to be remarkable for its capacity to decrease the rate of failures and inconclusive results in forensic casework. By using miniSTRs, the PCR efficiency is significantly improved as shorter PCR amplicons are generated with STR primers located closer to the repeat regions. In this article we aimed to present several practical considerations regarding the miniSTR genotyping for challenging forensic samples. Looking for a robust protocol to re-investigate some of our cases with inconclusive or no typing results we studied the efficiency of a miniSTR approach. We report by comparison our results obtained with a commercial miniSTR multiplex assay on samples previously tested with two different 16 STR commercial kits. Our conclusion is definitely in favor of including in the routine protocol the miniSTR assay as it was able to improve the results, providing better or even complete DNA profiles for the difficult samples where the conventional STR kits failed.

An assessment of preserved DNA in decomposed biological materials by using forensic DNA profiling

“…The results also show that peak height ratio, inter-colour balance and total peak height (which are profile quality parameters) observed in teeth are in agreement with the brain tissue. No amplification or dropout on the larger loci (more than 250 base pairs) included in the multiplex system suggest the need of the use of specifically designed kits for degraded DNA to achieve the amplification at these larger loci such as ABI Minifiler kit (Lopes et al 2009;Welch et al 2011;Constantinescu et al 2012). In this study, the effects of environmental variables were not controlled, since the samples were collected from a wide range of contexts.…”

Past, Present, and Future of DNA Typing for Analyzing Human and Non-Human Forensic Samples

“…However, some limitations and challenges are faced when dealing with highly degraded or low template DNA samples. To overcome these technical challenges, standardized mini-STR kits have been developed which use shorter versions of the core STRs and can be used in the same manner for forensic cases (Butler et al, 2007;Constantinescu et al, 2012). Keep in mind, DNA typing of humans -a single species -is the gold standard because of (a) the concerted scientific effort to standardize loci to analyze, (b) the development of commercial kits that can produce the same results regardless of instrumentation or laboratory performing the work, (c) a compatible and very large database that provides allelic frequencies for all sub-populations of humans, (d) standardized statistical methods used to report the results and (e) many court cases that have accepted human DNA typing evidence in a court of law -setting the precedent for future cases to use DNA typing results.…”

A short review on the use of short tandem repeat based DNA profiling in sexual assault

“…Analysis by conventional autosomal STR profiling revealed only the victim's profile. But, when mini STR profiling was proceeded, two profiles were generated, one from the victim and the other from the prime suspect in the case, highlighting the mini STRs' higher efficacy in generating profiles for all the contributors 24 .…”