Mutation rates in 21 autosomal short tandem repeat loci in a population from Goiás, Brazil

Abstract

The appearance of new mutations in polymorphic markers plays a central role in a range of genetic applications, including dating phylogenetic events, informing disease studies, and evaluating forensic evidence. The present study estimated the mutation rates of 21 autosomal STR loci in a population from Central Brazil. We studied 15 046 paternity cases from Goiás, Brazil from August 2012 to February 2015. We identified 262 mutations in the 21 loci. The loci that presented more mutations were FGA and D18S51, with a total of 46 and 28 mutations, respectively. The results showed mutational rates ranging from 1.7 × 10 to 7.6 × 10 mutations per site/region and the overall mutational rate was 2.1 × 10 ; these values were within the expected values for the STR markers. The most common type of mutation was one-step mutation, which totaled 96.2%. We found a higher rate of mutations of paternal origin (67.6%) than of mutations of maternal origin. The occurrence of mutations in STRs has important consequences for human identification, including the definition of criteria for exclusion in paternity testing and interpretation of genetic profiles in criminal cases.

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

“…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 ) .…”

“…We observed the highest STR mutation rates at loci vWA (2.8 × 10 −3 ), FGA and D18S51 (both with 2.7 × 10 −3 ), while loci TH01 and TPOX had no mutations. 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.…”

“…Vieira et al. observed a higher paternal rate but still quite many mutations of maternal origin, as did Sun et al. in a study analyzing Chinese and Brazilian populations, while Whittle et al.…”

Paternity testing using massively parallel sequencing and the PowerSeq™ AUTO/Y system for short tandem repeat sequencing

“…Sequences were analyzed and due to the repeat pattern of each sequence, it was possible to identify both mutations as paternal. The single step repeat gain/loss usually occurs due to slippage of the polymerase during replication, and this type of mutation is more likely to happen in paternal lineage cells due to the speed of cell divisions during spermatogenesis [14,15]. Mutations should be taken into account and the calculation of PI should be modified, for example using the models suggested by Brenner (http://dna-view.com/mudisc.htm) [11].…”

“…Mutations should be taken into account and the calculation of PI should be modified, for example using the models suggested by Brenner (http://dna-view.com/mudisc.htm) [11]. However, it is important to distinguish between mutations and exclusions and this can be achieved by analyzing more loci [15]. In both [12] 15…”