Mutation Analysis of STR Locus on 23 Autosomes in Hainan Population

[Objective] To analyze the mutation signature and regularity of STR locus on 23 autosomes in paternity testing cases in Hainan. [Methods] A total of 2715 paternity testing cases accepted by the Forensic Medical Identification Centre of our hospital from 2017 to 2020 derived from counties and cities in Hainan Province were collected, the cases containing gene mutations were selected, the mutation rate and details of each locus were counted, and the mutation regu-larity of 23 STR loci was analyzed. [Results] Of the 2715 cases identified as “support”, 1487 were triplet cases and 1640 were dyad cases, totaling 4614 meioses; There were 50 gene mutation events (including 17 triplet mutations and 33 dyad mutations), with an average mutation rate of 0.0047% and a cumulative mutation rate of 1.0837%. A total of 19 of the 23 STR loci were mutated, with a mutation rate of 0.1301% at the D12S391 locus and 0.0217% at five loci, TPOX, D1S1656, D2S441, D22S1045, and PentaD, while no muta-tion events were found at four loci, D19S433, TH01, D13S317, and D7S820. Of the 50 mutation events, 47 were one-step mutations, 1 was two-step, and 2 were three-step. There were 35 paternal mutations (13 triplets and 22 dyads), 6 maternal mutations (4 triplets and 2 dyads), and 9 indeterminate pater-nal/maternal mutations, with a paternal to maternal mutation ratio of 5.83:1. [Conclusion] The mutation rate of D12S391 locus is the highest, and the muta-tion rate of TPOX, D1S1656, D2S441, D22S1045 and PentaD loci is the lowest in Hainan population, and paternal mutations are more than maternal muta-tions. In the paternity test, if 1 - 3 STR loci do not conform to the genetic law, especially when the mutant locus is homozygous or the next of kin is identi-fied, it is necessary to use other kits to review and increase the number of loci or use the second-generation sequencing technology to confirm, carefully de-termine the mutation and ensure the accuracy of the identification conclusion.