Mutation rate estimates for 13 STR loci in a large population from Rio Grande do Sul, Southern Brazil

Abstract

Short tandem repeat (STR) polymorphisms have been extensively used in forensic genetics analysis. Knowledge about the locus-specific mutation rates of STRs improves forensic probability calculations and interpretations of diversity data. To incorporate single-locus diversity information into autosomal STR mutation rate estimations, 13 STR loci were studied during 2007-2009 in 10,959 paternity investigation cases from Rio Grande do Sul, the southernmost state of Brazil, covering an overall number of 284,934 allelic transfers. A total of 355 mutations were identified; 348 repeats were gains or losses of one step, three were gains or losses of two steps, and four were gains or losses of not stepwise mutation. The mutation rates ranged from 4.6 × 10(-5) to 2.3 × 10(-3), and the overall mutation rate estimate was 1.2 × 10(-3). The average of the paternal mutation rate (1.8 × 10(-3)) was five times higher than the maternal rate (0.36 × 10(-3)). The observed mutational features for STRs have important consequences for forensic applications, including the definition of criteria for exclusion in paternity testing and the interpretation of DNA profiles in identification analysis.

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.…”

“…The number of repeat units present in each allele was performed with ABI PRISM ® 3130xl Genetic Analyzer Data Collection v.3.0 and GeneMapper ID v.3.2.1 software (Applied Biosystems; Life Technologies, USA) was used for genotype identification. In order to comply with previous systems describing mutations, we assumed that the shortest step path from the paternal/maternal allele occurred to generate the child's discrepant mutated allele . We used the nomenclature recommended by the DNA Commission of the International Society of Forensic Genetics, as well as the recommendations for population data publication for forensic purposes .…”

Short Communication Y-STR haplotype diversity and population data for Central Brazil: implications for environmental forensics and paternity testing

“…Investigations of genetic links using database DNA has stood out in recent years (Chung and Fung, 2013;Mardini et al, 2013). Moreover, the study of human race has been of interest since ancient times.…”

“…Nowadays, considerable research has been conducted to identify the geographical origin of people and their closeness, from several points of view, as well as the degree of admixture in the genetic composition of a population. Therefore, the aim of this study was to determine the allele frequencies and haplotype diversity of Y-STRs in the population of Goias State, Central Brazil, and to compare the results with population data for samples from all Brazil regions (Mardini et al, 2013). …”