RESUMO
Objective T o observe and analyze the confirm ed cases of paternity testing, and to explore the m utation rules of ST R loci. Methods T he m utant ST R loci w ere screened from 20723 confirm ed cases of paternity testing by G oldeneye 20A system .T he m utation rates, and the sources, fragm ent length, steps and increased or decreased repeat sequences of m utant alleles w ere counted for the analysis of the characteristics of m utation-related factors. Results A total of 548 m utations w ere found on 19 ST R loci, and 557 m utation events w ere observed. T he loci m utation rate w as 0.07‰-2.23‰. T he ratio of pater-nal to m aternal m utant events w as 3.06:1. O ne step m utation w as the m ain m utation, and the num ber of the increased repeat sequences w as alm ost the sam e as the decreased repeat sequences. T he repeat se-quences w ere m ore likely to decrease in tw o steps m utation and above. M utation m ainly occurred in the m edium allele, and the num ber of the increased repeat sequences w as alm ost the sam e as the decreased repeat sequences. In long allele m utations, the decreased repeat sequences w ere significantly m ore than the increased repeat sequences. T he num ber of the increased repeat sequences w as alm ost the sam e as the decreased repeat sequences in paternal m utation, w hile the decreased repeat sequences w ere m ore than the increased in m aternal m utation. Conclusion T here are significant differences in the m utation rate of each locus. W hen one or tw o loci do not conform to the genetic law , other detection system should be added, and PI value should be calculated com bined w ith the inform ation of the m utate ST R loci in order to further clarify the identification opinions.