Genetic analysis of type 2 tri-allelic pattern at TPOX locus in the Chinese Han population

Tri-allelic patterns can occasionally be observed during the profiling of short tandem repeats (STRs) in routine forensic practice. In previous studies, the Type 2 tri-allelic pattern at TPOX has been widely studied in African and Brazilian populations. In this study, we investigated the incidence, rearrangement, and inheritance of the Type 2 tri-allelic pattern at the TPOX locus in a Chinese Han population. The frequency of the Type 2 pattern at TPOX was approximately 0.0189%, and the major extra allele was allele 11 in the Chinese Han population. Two major allelic combinations, 8/11 and 11/12, were observed, which are different from the configuration of that in both African and Brazilian populations. Tight linkage between alleles 11 and 12 was observed in the majority of the Type 2 pattern at TPOX in the Chinese Han population, while the location of the extra copy on chromosome 2 was validated, which shows an identical ancestral origin. The excess allelic combination 8/11 implies a homogeneous origin and tight linkage relationship. However, the rearrangement in the Type 2 pattern with the 8/11 allelic combination remained unknown. Altogether, these results show the configuration of the Type 2 tri-allelic pattern at the TPOX locus in the Chinese Han population, which will assist in the understanding of the Type 2 tri-allelic pattern at the TPOX locus in the global population.