Mutation rates for 20 STR loci in a population from São Paulo state, Southeast, Brazil

Abstract

Short tandem repeats (STRs) are genetic markers largely employed in forensic analysis and paternity investigation cases. When an inconsistency between the parent and child is considered as a possible mutation, the mutation rate should be incorporated into paternity index calculations to give a robust result and to reduce the chance of misinterpretation. The aim of this study was to estimate the mutation rates of 20 autosomal STRs loci used for paternity tests. In these loci we analysed 29,831 parent-child allelic transfers from 929 duo or trio paternity tests carried out during 2012?2016 from São Paulo State, Brazil. We identified 35 mutations in 16 loci, and they were more frequent in the paternal germline compared to the maternal germline. The loci with the highest rate were vWA and FGA and the ones with the lowest rate were PENTA E, PENTA D, D21S11, D7S820 and D6S1043. We did not identified any mutation in D2S1338, TH01, TPOX and D16S539 loci. All mutations consisted of losses or gains of one repeat unit. Mutation rates found in the São Paulo population have peculiarities, which justifies the use of regional databases in laboratories.

Slippage mutation rates in 15 autosomal short tandem repeat loci for forensic purposes in a Southeastern Brazilian population

“…Results obtained in the present study are similar to those reported in two other studies performed in Brazilian populations , regarding the paternal::maternal proportion of mutation origin. Our findings presented the mutation rate generated by paternal meiosis (1.8 × 10 −3 ) was six times higher than the maternal one (0.3 × 10 −3 ), even though we have detected 29 discrepant alleles with ambiguous origin (Table ).…”

“…Based on the number of meiosis per locus, the overall mutation rate determined in this study for the 15 forensic STR loci was 1.3 × 10 −3 (95% CI: 1.1–1.5 × 10 −3 ), which is a similar value to the findings of previous studies with Brazilian populations of the Southern and Southeastern regions , and with Polish and Southern Chinese Han populations, which ranged from 1,18 × 10 −3 to 1,39 × 10 −3 . The mutation rate calculated in this study is, however, slightly different from an earlier study including Southern, Southeastern and Central Brazilian populations (0.94 × 10 −3 ) and data published for the Northeastern region of the country (0.75 × 10 −3 ) , and much higher than the rate reported in a recent study analyzing a population from Central Brazil (0.21 × 10 −3 ) .…”

“…In previous studies performed in Southern and Central Brazil populations, vWA, FGA, and D18S51 were also the loci presenting the highest mutation rates, while TH01 and TPOX also presented very low mutation rates. Two other studies, one performed in a population from São Paulo and another one in Poland , reported the highest rates for vWA and FGA, with D12S391 and D5S818, being the third highest mutated loci, respectively. TH01 and TPOX did not present any mutation in both studies .…”

“…Two other studies, one performed in a population from São Paulo and another one in Poland , reported the highest rates for vWA and FGA, with D12S391 and D5S818, being the third highest mutated loci, respectively. TH01 and TPOX did not present any mutation in both studies . Another previous study performed in populations of Southern, Southeastern and Central Brazilian reported D10S1237 and D19S253 as those with the highest mutation rates, and no mutations in TH01 and TPOX.…”

“… obtained the paternal mutation rate five times higher than the maternal mutation rate and Martinez et al. reported the higher number of mutation in paternal inheritance compared to maternal inheritance (23 to 5, respectively).…”