Date of Submission

5-2026

Document Type

Thesis

Degree Name

Master of Science in Forensic Science

Department

Criminal Justice

Advisor

Heather Miller Coyle, Ph.D.

Committee Member

Claire L. Glynn, Ph.D.

Committee Member

Tina Moroose, M.S.

Keywords

Single Nucleotide Polymorphisms (SNPs), DNA Degradation, Fingernails, DNA Extraction, Genotyping, Phenotypic Traits

MeSH

Polymorphism, Single Nucleotide, Nails, DNA, Genotyping Techniques, Phenotype

LCSH

Single nucleotide polymorphisms--Forensic applications, Fingernails, DNA, Genotype-environment interaction, Phenotype

Abstract

Single nucleotide polymorphisms, SNPs, provide investigative leads in forensic science, yet limited research determines the reliability of these markers when exposed to external factors. SNP markers can indicate phenotypic traits, predisposition to diseases, how an individual's body may react towards medication, region-specific ancestry, etc. Current extraction techniques for human remains are invasive, typically extracted from bones or teeth. In low concentration, studies have shown that DNA can be extracted from fingernails for SNP marker analysis. This study records which SNP genotypes are commonly seen in populations, and tests the resilience of SNP markers extracted from fingernails when stored at 25 °C or 56 °C for 1 week, 2 weeks, 1 month, or 2 months. Fingernail samples were collected five times in two-week increments. SNP markers: rs12913832 on HERC2, rs1800407 on OCA2, and rs16891982 on SLC45A2 were examined from three populations: African American, Asian, and Caucasian. DNA was extracted from buccal swabs using the Invitrogen™ PureLink™ Genomic DNA Kit (Thermo Fisher Scientific, Waltham, MA), Applied Biosystems'™ Quantifiler HP and Trio DNA Quantification Kit was used for DNA quantitation (Life Technologies, Woolston, Warrington, UK), and SNPs were analyzed using Thermo Fisher's Custom TaqMan SNP Genotyping Assays (Life Technologies, Pleasanton, CA) protocol. Workflow was performed on the QuantStudio™ 5 Real Time PCR Instrument (Thermo Fisher Scientific, Foster City, CA). Fingernail samples were cleaned following a procedure by Allouche et al., DNA extraction was performed using the BcMag™ One-step Touch DNA Purification Kit (Bioclone, San Diego, CA), and quantitation and SNP marker analysis followed the same protocols as the buccal swabs. Buccal swabs, 35, and fingernail samples, 104, were collected. Fingernails needed to meet a threshold of 0.055g per sample for DNA extraction and a large autosomal concentration threshold of 0.090 ng/uL for SNP marker analysis. SNP genotyping was successful at most time points and temperatures with a 96% accuracy rate.

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