Novel Tri-Allelic Pattern at Penta E Locus Identified in Parentage Testing

In a parentage testing case report published in the International Journal of Legal Medicine, forensic researchers identified a novel Type I tri-allelic pattern at the autosomal short tandem repeat locus Penta E in a Chinese family. The atypical genotyping profile presented three distinct alleles—designated 13, 19, and 20—which had not been previously documented in the STRBase database. While short tandem repeat typing serves as a standard tool in parentage testing and forensic identification, atypical tri-allelic configurations involving three alleles at a single locus complicate routine forensic interpretation.

To verify the authenticity of the atypical profile, the investigators performed re-amplification using a different commercial kit alongside sequencing validation. These laboratory procedures confirmed that the observed genotype represented a genuine Type I tri-allelic pattern resulting from a somatic mutation.

The researchers further examined biological specimens from different tissue sources, analyzing the peak height ratios of the three imbalanced alleles at the Penta E locus across blood, oral swabs, and hair with follicles. The distribution of these peak height ratios among the examined tissues suggested that the underlying somatic mutation occurred during embryonic differentiation between the ectoderm and mesoderm layers.

To evaluate biological relatedness despite the anomalous profile, the maternity index for the Penta E locus was calculated using two distinct approaches, with both calculations supporting the parent-child relationship. The investigators reported that this case elucidates the formation mechanism of tri-allelic patterns, contributes valuable empirical data for refining kinship testing and evidence evaluation in forensic practice, and highlights the ongoing need for standardized interpretation guidelines in forensic casework.

Subject of Research: Forensic genetics and tri-allelic STR pattern identification in parentage testing

Article Title: Identification of a tri-allelic pattern at the Penta E locus in a case of parentage testing

Article References: Feng, W., Zhao, G., Chen, J., Zheng, Z., & Xu, Q. (2026). Identification of a tri-allelic pattern at the Penta E locus in a case of parentage testing. International Journal of Legal Medicine. https://doi.org/10.1007/s00414-026-04069-5

Image Credits: AI Generated

DOI: 10.1007/s00414-026-04069-5

Keywords: Penta E locus, tri-allelic pattern, Type I pattern, parentage testing, short tandem repeat typing, somatic mutation, forensic identification, STRBase, maternity index, kinship testing, ectoderm differentiation, mesoderm differentiation, peak height ratios, oral swabs, hair follicle analysis, sequencing validation, case report, Chinese family