The mutation of short tandem repeat (STR) loci is affected by several factors, such as sex, age, and DNA architectures. Previous studies have shown a different profile of mutation rates at autosomal STR loci among populations. It is important to provide population data and reveal underlying factors influencing the evaluation of STR mutation rates. In this study, we performed a comprehensive analysis on the mutation of 19 autosomal STR loci through 124,773 parent-child allelic transfers from 5846 paternity testing cases. A total of 197 mutations were observed including 187 single-step mutations. The observed mutation rates ranged from 0.15 × 10-3 (TH01) to 4.57 × 10-3 (FGA), and the average mutation rate across all the 19 loci was 1.58 × 10-3. Furthermore, the average mutation rate of STR loci increases with the paternal conception ages and remains relatively stable in different maternal age groups, which suggest the profile of paternal conception ages as a potential factor influencing the evaluation of STR mutation rates and the ratio of paternal versus maternal mutation rate in populations. Multidimensional scaling analysis (MDS) shows a difference in the profile of mutation rates at 13 CODIS STR loci among ethnical groups. Based on our data, our results support that short alleles are biased towards expansion mutation and longer alleles favor contraction mutation. In conclusion, our results provide useful information for further investigation on STR mutation in forensic genetics and population genetics.
Keywords: Mutations; Paternity testing; Population genetics; Short tandem repeats.