Mutation analysis of 28 autosomal short tandem repeats in the Chinese Han population

Short tandem repeats (STRs) have been extensively used in forensic genetics. However, according to previous studies, the mutation rates of STRs are relatively high and are affected by many factors. Therefore, it is important to analyze STR mutations and determine the influence of underlying factors on STR mutation rates. Mutation rates of 28 autosomal STRs were determined from 8708 paternity testing cases in the Chinese Han population, and the relationships between STR mutation rates and population, sex, age, allele length and heterozygosity were investigated. A total of 279 mutations were observed at 27 loci in a total of 233,530 meiosis cases, including 273 (97.8%) one-step, 5 (1.8%) two-step and 1 (0.4%) three-step mutations. The overall average mutation rate was 1.19 x 10(-3) (95% CI 1.06 x 10(-3) - 1.34 x 10(-3)) ranging from 0 (TPOX) to 2.79 x 10(-3) (D13S325). Mutation rate comparisons revealed statistically significant differences at several STRs among populations. Paternal mutations occurred more frequently than maternal mutations, at a ratio of 6.04:1, and the mutation rate tended to increase with paternal age. Moreover, our study revealed a bias towards contraction mutations for long alleles and expansion mutations for short alleles. No obvious bias was observed in the overall mutation direction. In addition, STR loci with higher expected heterozygosity (H-exp) tended to have higher mutation rates. This work revealed the relationships between STR mutation rates and several influencing factors, providing useful data and information for further research on STR mutations in forensic genetics.

Automated summary

This study investigated the mutation rates of 28 autosomal STRs in the Chinese Han population, revealing relationships between STR mutation rates and factors such as population, sex, age, allele length, and heterozygosity. The results showed a higher frequency of paternal mutations compared to maternal mutations, an increase in mutation rate with paternal age, a bias towards contraction mutations for long alleles, and expansion mutations for short alleles, with no overall bias in mutation direction. Additionally, loci with higher expected heterozygosity tended to have higher mutation rates, providing valuable information for further research on STR mutations in forensic genetics.