Browsing by Author "Gomes, Iva"
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- Genetic characterization of Guinea-Bissau using a 12 X-chromosomal STR system: inferences from a multiethnic populationPublication . Gomes, Iva; Pereira, Plácido J.P.; Harms, Sonja; Oliveira, Andréa M.; Schneider, Peter M.; Brehm, AntónioA male West African sample from Guinea-Bissau (West-African coast) was genetically analyzed using 12 X chromosomal short tandem repeats that are grouped into four haplotype groups. Linkage disequilibrium was tested (p ≤ 0.0008) and association was detected for the majority of markers in three out of the four studied haplotype clusters. The sample of 332 unrelated individuals analyzed in this study belonged to several recognized ethnic groups (n = 18) which were used to evaluate the genetic variation of Guinea-Bissau’s population. Pairwise genetic distances (FST) did not reveal significant differences among the majority of groups. An additional 110 samples from other countries also belonging to West Africa were as well compared with the sample of Guinea-Bissau. No significant differences were found between these two groups of West African individuals, supporting the genetic homogeneity of this region on the X chromosome level. The generation of over 100 DNA West African sequences provided new insights into the repeat sequence structure of some of the present X-STRs. Parameters for forensic evaluation were also calculated for each X-STR, supporting the potential application of these markers in typical kinship scenarios. Also, the high power of discrimination values for samples of female and male origin observed in this study, confirms the usefulness of the present X-STRs in identification analysis.
- New sequence variants detected at DXS10148, DXS10074 and DXS10134 lociPublication . Gomes, Iva; Brehm, António; Gusmão, Leonor; Schneider, Peter M.A great amount of population and forensic genetic data are available for X-STRs supporting the need for having a common and accurate nomenclature among laboratories allowing for better communication, data exchange, and data comparison. DXS10148, DXS10074 and DXS10134 are commonly used X-STRs particularly due to their inclusion in the commercial kit Investigator Argus X-12 (Qiagen). Samples from West Africa and Iraq were sequenced for all three X-STRs allowing the detection of new DNA sequence variants. At DXS10148, variation was detected at four bases downstream from the flanking region from the repeat motif. The sequence AAGG-AAAG has been detected for the first time as a varying (AAGGAAAG)1–3 motif, in the present work. One additional string when compared to the common one (AAGGAAAG)2 adds eight bases to the fragment size of the tetranucleotide STR. This means that 2 repeats are added in these cases to the fragment size of the allele, while the presence of only one copy will reduce the expected allele size by 2 repeats. At DXS10074 two varying stretches consisting of AC and AG dinucleotide repeats were observed in the upstream flanking region, six bases from the main repeat core that also influence the expected allele size. DXS10134 revealed a simpler nomenclature in the Guinea-Bissau sample set when compared to the previously described allele nomenclature. This detected new hidden variation also has impact on the actual allele nomenclature at this locus as it contributes to a new class of short alleles so far undetected in other studies.