Exploring New Short Tandem Repeat Markers for DNA Mixture Deconvolution

• NCJ Number: 255133
• Author(s): Nicole M. Novroski
• Date Published: August 2020
• Length: 12 pages
• Agencies: NIJ-Sponsored
• Award: Enhancing Mixture Interpretation with Highly Informative STRs

Annotation

The incorporation of new forensic markers coupled with the integration of new technologies and chemistries that enable the forensic analyst to quantify component contributor alleles in DNA mixture samples has the potential to revolutionize the approach to DNA mixture interpretation and resolve more crimes.

Abstract

Relying on their polymorphic nature, short tandem repeats (STRs) have been extensively studied and routinely utilized as human identity markers in forensic genetics; however, even the most comprehensive STR multiplexes in use today are limited in their ability to determine the number and appropriation of component contributor alleles in DNA mixtures. The difficulty in parsing out individuals in DNA mixtures is a consequence of overlapping length-based alleles genotyped using the polymerase chain reaction (PCR) coupled with capillary electrophoresis (CE). Many challenges exist in the resolution of minor alleles (i.e., the alleles originating from a minor contributor) from stutter and stochastic effects (e.g., inherent heterozygote peak imbalance, undetected alleles [drop out]) in a given DNA profile, in addition to the complex statistical models and algorithms necessary to render DNA mixtures interpretable from a forensic casework standpoint; therefore, we can either adapt to complex interpretation methods, or pursue new bench science approaches to DNA mixture deconvolution. One promising area of research includes the incorporation of additional highly polymorphic STR loci to complement current marker multiplexes and has great potential to improve the forensic genetic analysis of DNA mixtures. (publisher abstract modified)