Case Analysis of 44 Autosomal STR Ternary Allele Genotypes

DOI: https://doi.org/10.62517/jmhs.202605117

Author(s)

Yingwen Wang, Shaoni Zhang*, Shalin Chen, Xinmin Ma

Affiliation(s)

Guangdong Boxin Forensic Identification Institute, Shanwei, Guangdong, China *Corresponding Author

Abstract

This study investigates the distribution characteristics and genetic mechanisms of three-allele genotypes at STR loci. Using the PowerPlex 21 Amplification Kit and the Human DNA Typing Kit (Platinum) from Shenzhen Huada Forensic Technology Co., Ltd., 44 cases of three-allele genotypes identified in routine paternity testing cases handled by our institute from 2018 to 2025 were analyzed to summarize their distribution and genetic features. Results: The D6S1043, D5S818, D12S391, and vWA loci were detected in 1 case each; the D19S433, D8S1179, D78S820, TPOX, and CSFIPO loci were detected in 2 cases each. The D18S51 locus was detected in 3 cases, the Penta E locus in 6 cases, the D21S11 locus in 10 cases, and the Penta D locus in 11 cases. The three-allele genotypes at the Penta E, D21S11, and PentaD loci were relatively common. Patients with trisomy 21 were found to have type II three-allele genotypes at both the PentaD and D21S11 loci. In forensic DNA analysis, Type 1 tri-allelic pattern refers to the phenomenon of three alleles appearing at a single locus, typically caused by chimerism or somatic mutation. Chimerism and sampling procedures can indeed affect the ratio of the original gene to the mutated gene, leading to various forms of tri-allelic peak patterns, but the peak height of the dominant allele is the sum of the other two. The formation of Type 2 tri-allelic patterns may originate from non-allelic homologous recombination. This study provides statistical analysis of tri-allelic data from routine cases, offering data for research on the genetic characteristics of STR tri-allelic patterns.

Keywords

Short Tandem Repeat; Three-Allele Genotype; Genetic Mechanism

References

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