Thesis

Population genetic analysis of forensic DNA markers in the Nigerian population

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T17586
Person Identifier (Local)
  • 201886717
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • Nigeria, located in West Africa within sub-Saharan Africa, is the continent’s most populous Black nation and ranks as the seventh most populated country globally. It is home to three major ethnic groups: Igbo, Yoruba, and Hausa-Fulani. A thorough study of population genetics is essential for accurately interpreting forensic genetic evidence in criminal investigations. The genetic composition of these ethnic groups has not been extensively investigated compared to global reference populations. This project collected blood samples from 303 unrelated individuals from Nigeria's three major ethnic groups using FTA® cards. The genetic analysis utilised three kits: the 17-locus QIAGEN™ Investigator® ESSplex SE QS Kit and the 21-locus GlobalFiler™ Express Kit for autosomal STRs, along with the 23-locus Promega PowerPlex® Y23 System Kit for Y-chromosomal STRs. Of the 303 blood samples, 167 male samples were analysed for Y-STRs, while all 303 were analysed for autosomal STRs. The autosomal STR data was then analysed to determine forensic parameters, F statistics, and Hardy-Weinberg equilibrium. Population structure analysis was also conducted to assess inter-subpopulation differentiation using STRUCTURE, principal component analysis, and neighbour-joining methods. A total of 606 allele calls were obtained from 16 autosomal STR loci using the QIAGEN™ Investigator® ESSplex SE QS Kit and 21 autosomal STR loci using the GlobalFiler™ Express Kit. The allele frequencies were calculated for the entire population and for each ethnic group individually. The QIAGEN™ Investigator® ESSplex SE QS Kit analysis showed SE33 as the most informative, followed by D2S1338, while TH01 had the fewest allelic variants. Similarly, the GlobalFiler™ Express Kit indicated SE33 as the most informative, with D2S1338 next, but D13S317 had the lowest allelic variants. Both kits had a combined power of discrimination and exclusion exceeding 99.999%. The 21-locus GlobalFiler™ Express Kit, which had no off-ladder alleles and more markers, offered higher discriminatory power, improved likelihood ratios, and lower random match probabilities than the 16-locus QIAGEN™ Investigator® ESSplex SE QS Kit. The STRUCTURE, principal component analysis, neighbour-joining, and FST analyses revealed no genetic differences among the Igbo, Yoruba, and Hausa-Fulani ethnic groups based on autosomal STR data from the QIAGEN™ Investigator ESSplex SE QS Kit and the GlobalFiler™ Express Kit. The Promega PowerPlex® Y23 System Kit analysis identified the DYS385a/b locus as the most informative, while the DYS391 locus had the lowest levels of polymorphic information content, gene diversity, and discrimination capacity. Overall, haplotype diversity and discrimination capacity across all 23 loci were found to be 99.4% and 99.9%, respectively. Principal component and neighbour-joining analyses suggest that the Igbo and Yoruba ethnic groups share a paternal lineage, while a subset of the Hausa-Fulani group appears distinct, indicating admixture. The three subpopulations also showed differences in linkage disequilibrium across specific locus pairs. The study analysed inter-population genetic distances across five continents, involving 7,664 unrelated people from 24 populations using autosomal STR markers and 7,348 unrelated individuals from 50 populations using Y-STR markers. Y-STR results show Nigerian populations are genetically closely aligned with other West African groups (Niger-Congo) at the continental level but genetically distinct from North African (Afroasiatic), East African (Nilotic), and Indigenous Central African (Pygmy, Khoisan) populations. Autosomal STR findings placed Nigeria within the African clade, with closer ties to diaspora populations in North and South America. This research highlights the forensic implications of population differences and the importance of establishing a national DNA repository and allele frequency data for Nigeria.
Advisor / supervisor
  • Haddrill, Penelope
Resource Type
DOI
Date Created
  • 2025

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