Ethiopian DNA Study Maps Forensic Markers in Addis Ababa

Researchers have generated a comprehensive genetic reference database for the population of Addis Ababa, Ethiopia, by analyzing 24 autosomal short tandem repeat loci in 605 unrelated individuals. Published in the Egyptian Journal of Forensic Sciences, the study provides critical allele frequency data that can improve the accuracy of forensic individual identification and paternity testing in the region. The findings indicate that the tested genetic markers possess high polymorphism, making them suitable for distinguishing between individuals in the diverse urban population of Ethiopia’s capital.

The study was led by a team including Feifei Gao, Abiy Wendifraw Assefa, and Chunxia Yan, among others, who sought to address a gap in forensic genetic data for the Addis Ababa population. While Ethiopia is widely recognized for its role in human evolution and possesses a rich hominid fossil record, genetic studies focusing specifically on the forensic characteristics of the Addis Ababa population had remained sparse. The city’s demographic complexity, shaped by internal migration from various Ethiopian regions and ethnic groups, means that existing datasets from single regional or ethnic groups may not fully represent the genetic diversity of the capital’s residents.

Short tandem repeats, also known as microsatellites, are nucleotide repeats of 2 to 6 base pairs located predominantly in noncoding regions of the human genome. These markers account for approximately 3% of the genome and are characterized by high heterozygosity and codominant inheritance. Because of these properties, autosomal STRs are pivotal in forensic science for convicting offenders, exonerating the innocent, and identifying victims of crimes or disasters. Population-specific allele frequency databases are essential for calculating forensic statistical indices such as power of discrimination, matching probability, and power of exclusion, which are necessary for reliable statistical interpretation in legal cases.

The study collected dried blood spot samples from 605 unrelated, healthy volunteers at the Addisu Gebeya Health Centre in Addis Ababa. The participants were associated with the Ethiopian Red Cross Society, and informed consent was obtained from all individuals. The sample included 440 females and 165 males. Regarding ethnic composition, 401 donors were of Oromo ethnicity, 199 were of Amhara ethnicity, and ethnicity information was unavailable for the remaining five donors. The study protocol was reviewed and approved by the Biomedical Ethics Committee of Health Science Centre, Xi’an Jiaotong University, China, ensuring ethical compliance in the collection and analysis of genetic material.

Genomic DNA was extracted from the dried blood spot samples using a standardized kit and quantified using a fluorometer to ensure quality control. PCR amplification of the 24 STR loci was performed using a multiplex amplification system, specifically the HUMDNA TYPING (Yanhuang) kit. The amplification process involved precise thermal cycling conditions to ensure the efficient generation of DNA fragments for analysis. Capillary electrophoresis was then conducted using an ABI 3500xL Genetic Analyzer to separate the DNA fragments based on size. Alleles were assigned by comparison with an allelic ladder, and only complete and concordant STR profiles that passed all quality-control criteria were included in the final statistical analyses.

A total of 378 distinct alleles were observed across the 24 STR loci in the Addis Ababa population. The allele frequencies ranged from 0.0008 to 0.4678, indicating significant genetic variation. The number of alleles per locus varied, with D13S317 showing the fewest at 8 alleles and SE33 showing the most at 45 alleles. The mean number of alleles per locus was 14. Statistical analysis revealed that all 24 loci were in Hardy-Weinberg equilibrium after Bonferroni correction for multiple testing, and no significant linkage disequilibrium was detected among the pairwise loci. This suggests that the loci can be treated as independently inherited markers for forensic calculations.

The forensic statistical indices demonstrated that the 24 STR loci are highly informative for the Addis Ababa population. The SE33 locus exhibited the highest power of discrimination, while D22S1045 showed the lowest. The combined power of discrimination for all 24 loci was greater than 0.999999999, indicating an extremely high capacity to distinguish between individuals. Similarly, the combined power of exclusion was greater than 0.999999999, and the combined match probability was 3.33707 × 10−19, further confirming the strong discriminatory power of the panel.

Beyond forensic applications, the study examined the population genetic relationships of the Addis Ababa population using multidimensional scaling and phylogenetic reconstruction. Based on 13 overlapping A-STR loci, the Addis Ababa population was found to be genetically close to several African or African-descendant populations, particularly Sudan and Colombia-African. In the multidimensional scaling plot, the Addis Ababa population was located near these groups, while Morocco and Egypt were separated from most other populations. The unweighted pair-group method with arithmetic means phylogenetic tree placed the Addis Ababa population within a branch containing African or African-descendant populations, including Sudan, Tanzania, Angola, and Karamoja-Uganda.

The observed genetic proximity to Sudan is geographically plausible given the regional connections within Northeast Africa and the Horn of Africa. The intermediate position of the Addis Ababa population in the multidimensional scaling plot may reflect the complex genetic background of Ethiopian populations and the geographic location of Ethiopia as a key gateway for early interactions between the African continent and Eurasia. However, the researchers noted that these interpretations should be considered cautiously because the population comparisons were based on a limited number of overlapping loci. The results suggest broad population-level genetic relationships rather than detailed demographic or ancestry inferences.

The study highlights several limitations that should be considered when interpreting the findings. Although 605 unrelated individuals were included, the Addis Ababa population is highly diverse, and future studies with broader sampling of different ethnic and regional backgrounds would provide a more comprehensive representation. Additionally, the population comparisons were performed using only 13 overlapping A-STR loci, which may limit the resolution compared with genome-wide single nucleotide polymorphism data or larger STR panels. STR-based analyses are useful for forensic reference purposes and broad population comparisons but are not designed to infer detailed demographic history.

The findings contribute to a more comprehensive understanding of genetic diversity in Ethiopia and the Horn of Africa. By establishing a population-specific STR reference database for Addis Ababa, the study supports local and regional forensic practice and improves the reliability of forensic statistical interpretation in local casework. The dataset can serve as a reference for forensic individual identification and paternity testing, as well as for population genetics studies. The researchers recommend further studies integrating expanded STR panels, single nucleotide polymorphism data, and additional Ethiopian populations to clarify the genetic structure of the Addis Ababa population and to enhance the forensic utility of these markers.

This research underscores the importance of population-specific genetic data in forensic science, particularly in regions with high genetic diversity. The high polymorphism of the 24 STR loci in the Addis Ababa population ensures that they can be effectively used to distinguish between individuals in forensic investigations.

Subject of Research: Genetic polymorphism of 24 short tandem repeats in the population of Addis Ababa, Ethiopia

Article Title: Genetic polymorphism of 24 short tandem repeats in the population of Addis Ababa, Ethiopia

Article References: Gao, F., Assefa, A. W., Yang, X., Paul, G., Hou, B., Zhang, Y., Liu, J., Xie, S., Zhang, B., & Yan, C. (2026). Genetic polymorphism of 24 short tandem repeats in the population of Addis Ababa, Ethiopia. Egyptian Journal of Forensic Sciences, 16(1), Article 72. https://doi.org/10.1186/s41935-026-00571-4

Image Credits: AI Generated

DOI: 10.1186/s41935-026-00571-4

Keywords: Genetic, polymorphism, short, tandem, repeats, population, Addis, Ababa, Ethiopia, scientific research