SNP-based DNA Forensics
We have received a one-year, $54,913 grant from the Midwest Forensics Resource Center (MFRC) to research
testing DNA samples for population of origin using single nucleotide polymorphisms (SNPs).
Our Specific AIMs
Our goal is to develop and help implement a new forensic technique using available equipment in the crime laboratories of the
St. Louis County Police,
the St. Charles County Sheriff, and
the Missouri Highway Patrol.
This "population test" will genotype ancestry-informative single nucleotide polymorphisms (SNPs) and compare the results with known population frequencies
of self-described ethnic groups to narrow the possible ancestry of a sample.
Specifically, we aim to:
- Generate a set of ancestry-informative markers (AIMs) and identify a subset that will be sufficiently powerful for the population test.
- Assemble components of the population test, including chemistry and analysis tools, and validate them by characterizing additional sets of DNAs.
- Assist collaborators in implementing the population test, including providing components, protocols, and technical advice.
- Publicize the population test to the wider forensics community.
Progress Reports Submitted to Midwest Forensics Resource Center
We submitted updates
on our forensic SNPs research to the MFRC in
August 2007
and in
November 2007 .
Genotyping SNPs to Infer the Population-of-Origin of a Forensic Sample
There are at least 400 human SNPs that are
assayable in almost any forensics laboratory and highly informative on continent of origin of forensic DNA samples.
As a proof of principle, we selected 18 of the most informative markers (all with ABI TaqMan assays) for
in silico validation using HapMap genotype data.
Figure 1 (below) shows the probability assessment for the HapMap "YRI" panel, comprised of 96 Yoruba tribe individuals from Nigeria.
YRI genotypes at the 16 loci correctly determined African/African-American as the most likely population of origin for these samples.
Our results demonstrate that
SNPs have the power to discriminate between 9 populations of possible origin by calculating conditional probabilities from a sample's genotypes.
Please see the complete study.
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Figure 1.
Population log scores for YRI samples based on their genotypes at the 16 loci.
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Population abbreviations: EUA=European-American; AFR=African; AMI=American Indian; EAS=East Asian; SAS=South Asian; AFA=African-American; PRN=Puerto Rican; MAM=Mexican-American; MXN=Mexican
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Literature on Ancestry-informative Markers and Forensic SNPs
Yang, N., et al., Examination of ancestry and ethnic affiliation using highly informative diallelic DNA markers: application to diverse and admixed populations and implications for clinical epidemiology and forensic medicine. Hum Genet, 2005. 118(3-4): p. 382-92.
Rosenberg, N.A., et al., Informativeness of genetic markers for inference of ancestry. Am J Hum Genet, 2003. 73(6): p. 1402-22.
Kidd, K.K., et al., Developing a SNP panel for forensic identification of individuals. Forensic Sci Int, 2005.
Collins-Schramm, H.E., et al., Mexican American ancestry-informative markers: examination of population structure and marker characteristics in European Americans, Mexican Americans, Amerindians and Asians. Hum Genet, 2004. 114(3): p. 263-71.
Barnholtz-Sloan, J.S., et al., Informativeness of the CODIS STR loci for admixture analysis. J Forensic Sci, 2005. 50(6): p. 1322-6.
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