【Objective】 To observe the mutation events of short tandem repeat (STR) loci in 10 000 parentage confirmed trio-cases and obtain the mutation rates of STR loci. 【Methods】 15 STR loci of 10 000 parentage confirmed trio-cases were genotyped with PowerPlexTM16 system and the cases containing mutant STR loci were screened. The sources and steps of mutant alleles were ascertained. The locus-specific

paternal or maternal specific and allele-specific mutation rates with the corresponding 95% CIs were calculated

respectively. The characteristics of the mutations were analyzed. 【Results】 368 mutant cases

a total of 379 mutation events were observed in 10 000 trio-cases for these 15 STR loci. The incidence of mutant cases was 3.68%. The mutation rates of 15 STR loci were between 0.10 × 10-3 ~ 2.30 × 10-3

and the average mutation rate was 1.26 × 10-3. The paternal and maternal mutation rates were 0.05 × 10-3 ~ 1.35 × 10-3 and 0.05 × 10-3 ~ 0.70 × 10-3

respectively. The allele-specific single-step mutation rates for FGA

vWA and D18S51 were between 5.0 × 10-5 ~ 40.0 × 10-5

5.0 × 10-5 ~ 50.0 × 10-5 and 5.0 × 10-5 ~ 35.0 × 10-5

respectively. The ratios of paternal to maternal mutant events for these 15 STR loci were between 1.3 ∶ 1 ~ 17.0 ∶ 1

and the average ratio was 3.57∶1. 【Conclusion】 STR mutation was commonly existed in paternity testing. The mutation rates of various loci

paternal and maternal sources

and various alleles showed significant differences. It was necessary to obtain these data to accurately interpret the genotyping results in paternity testing.