Allele frequencies of three STRs of the human von Willebrand factor gene (vWF) in a Brazilian population sample.

Allele frequencies were calculated for three tetrameric short tandem repeats (STRs) located in intron 40 of the human von Willebrand factor (vWA, vWF1 and vWF2) in 352 white individuals sampled from an urban population from the northeastern region of the State of São Paulo, Brazil. The exact test did not indicate any significant deviation from HWE for any of the three investigated loci. The allele frequencies of vWA and vWF1 showed unimodal and bimodal distributions, respectively, and the frequencies of vWF2 in our sample exhibited bimodal or even trimodal patterns. These differing patterns could reflect the differential action of one selective factor or of the distribution of mutations in these STRs, although the STRs are very close to one another and belong to the same gene. The frequency of paternity exclusions observed for each of these three loci conform to the theorectical expectations. The lack of difficulties regarding the methodology of typing and the forensic value of statistical parameters confirm the usefulness of these systems to study Brazilian populations.