A novel set of DIP-STR markers for improved analysis of challenging DNA mixtures. (November 2015)

• Record Type: Journal Article
• Authors: Oldoni, Fabio; Castella, Vincent; Hall, Diana
• Is Part Of: Forensic science international. Volume 19(2015:Nov.)
• Page Start: 156
• Page End: 164
• Publication Date: 2015-11
• Subjects: Compound genetic marker -- DNA mixtures -- Insertion/deletion -- Allele-specific PCR -- Touch DNA; Forensic genetics -- Periodicals; Génétique légale -- Périodiques; Forensic genetics; Electronic journals; Periodicals; 614.1
• DOI: 10.1016/j.fsigen.2015.07.012
• Languages: English
• ISSNs: 1872-4973

Abstract

Highlights: A novel set of 10 DIP-STR markers for unbalanced DNA mixture resolution is presented. They are short (146–271 bp), do not include dinucleotide STRs, are not gender-specific. They require as low as 0.03–0.1 ng of DNA template and can resolve DNA ratios of 1:1000. Population data ( N = 103) and tests on simulated DNA mixtures are provided. These novel DIP-STRs may empower the analysis of so far underused biological evidence. Abstract: Currently available molecular biology tools allow forensic scientists to characterize DNA evidence found at crime scenes for a large variety of samples, including those of limited quantity and quality, and achieve high levels of individualization. Yet, standard forensic markers provide limited or no results when applied to mixed DNA samples where the contributors are present in very different proportions (unbalanced DNA mixtures). This becomes an issue mostly for the analysis of trace samples collected on the victim or from touched objects. To this end, we recently proposed an innovative type of genetic marker, named DIP-STR that relies on pairing deletion/insertion polymorphisms (DIP) with standard short tandem repeats (STR). This novel compound marker allows detection of the minor DNA contributor in a DNA mixture of any gender and cellular origin with unprecedented resolution (beyond a DNA ratio of 1:1000). To provide a novel analytical tool useful in practice to common forensic laboratories, this article describes the first set of 10 DIP-STR markers selected according to forensic technical standards. The novel DIP-STR regions are short (between 146 and 271 bp), include only highly polymorphic tri-, tetra- and pentanucleotide tandem repeats and are located on different chromosomes or chromosomal arms to provide statistically independent results. This novel set of DIP-STR can target the amplification of 0.03–0.1 ng of DNA when mixed with a 1000-fold excess of major DNA. DIP-STR relative allele frequencies are estimated based on a survey of 103 Swiss individuals. Finally, this study provides an estimate of the occurrence of informative alleles and a calculation of the corresponding random match probability of the detected minor DIP-STR genotype assessed across 10, 506 pairwise conceptual mixtures.