Development of a polymorphic short tandem repeat locus multiplex system for efficient human identification.

This study aimed to develop a short tandem repeat (STR) multiplex system, made up of 22 highly informative STR loci, for application in forensic genetics. The system comprised 21 polymorphic autosomal loci (D3S1358, TH01, D21S11, D18S51, Penta E, D5S818, D13S317, D7S820, D16S539, CSF1PO, Penta D, vWA, D8S1179, TPOX, FGA, D2S441, D17S1301, D19S433, D18S853, D20S482, and D14S1434) and the amelogenin gene locus. Strategies were developed to overcome the challenges involved in creating a multiplex system. Based on the literature and available databases, the STR loci were selected with the aim to obtain discriminatory markers, and followed specific criteria for this purpose. Primers were projected using the Primer3 software, and AutoDimer was used to evaluate possible interactions between them. The 22 selected STR loci were validated individually and jointly, both to assess their sensitivity and to test the efficiency of the multiplex system. Statistical analyses were based on the genetic data of 450 unrelated individuals living in the State of Goiás, thus allowing the establishment of the parameters necessary to use this system. A total of 239 alleles were detected for the 22 loci in the set, allowing for a probability of identity of 4.23 x 10-25 to be obtained. The combined power of discrimination was 0.999999999999999999999999 and the combined power of exclusion was 0.99999. Upon complete validation of the entire system, this multiplex assay was considered to be a powerful tool for application in human identification by DNA analysis.

Allele frequencies of combined DNA index system (CODIS) and non-CODIS short tandem repeat loci in Goiás, Central Brazil.

In studies of human identification, obtaining a high standard of outcomes and satisfactory conclusions are directly related to the use of highly polymorphic molecular markers. In addition to the combined DNA index system (CODIS) group, it is also important to implement non-CODIS markers into the analysis, as they increase the power of discrimination. During the identification process, it is essential to consider the genetic variation among distinct groups of populations, as the allele frequencies are directly associated with the power of discrimination. However, the population of Goiás, a State located in Central Brazil, is characterized by a highly mixed population due to its diverse ethnic origins. In this study, a survey of the allelic frequencies in the Goiás population was carried out using a molecular assembly composed of 21 autosomal loci both from and external to the CODIS group. The new data, for some of the markers used, were statistically similar to those from previous studies. This consistency means that the use of these markers might serve as a parameter for future population comparisons. The results from these analyses further our knowledge of the study of human identification.

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

The central region of Brazil was colonized by internal migration of individuals of different origins, who contributed to the genetic diversity existing in this population. This study determined the allele frequencies and haplotype diversity of Y-STRs in Goiás State, Central Brazil, and compared the data obtained with a sample of the Brazilian population, consisting of individuals from the five geographical regions of Brazil. A total of 353 males were typed for 12 Y-chromosome short tandem repeat (Y-STR) markers. We selected males who had no degree of relatedness, from the five mesoregions of Goiás State. DNA was extracted from blood samples followed by the amplification of the 12 Y-chromosome loci. The products were analyzed to obtain the allele profiles on an ABI3500 automated sequencer using the Gene Mapper software. Allele frequencies and haplotype diversity were estimated by direct counting, and gene diversity for each locus was computed using the Arlequin software. The results are consistent with the history of miscegenation of the population of Central Brazil, in which we observed 321 different haplotypes. The average gene diversity at the 12 loci was 0.645. DYS385b and DYS389I showed the highest (0.704) and lowest (0.520) genetic diversity values, respectively. The FST value between the Brazilian and Goiás populations was 0.00951, showing no statistical significance. The results of this study allowed the establishment of haplotypes found in the forensic samples of Goiás State serving as a reference in the elucidation of criminal cases and paternity tests, as well as population and evolutionary inferences.

Tracking microdeletions of the AZF region in a patrilineal line of infertile men.

Male infertility is considered to be a difficult-to-treat condition because it is not a single entity, but rather reflects a variety of different pathologic conditions, thus making it difficult to use a single treatment strategy. Structural alterations in the Y chromosome have been the principal factor responsible for male infertility. We examined 26 family members of 13 patients with male infertility who showed deletions in the AZF region. In family 1, the father and a brother did not show microdeletions. However, a son showed a microdeletion in AZFa (sY84) and an azoospermic sperm analysis, but another son had a microdeletion in AZFa (sY84) and AZFb (sY127) and a normal sperm analysis. The father of family 2, with severe oligozoospermia, had a microdeletion in the AZFa region (sY84) and his son, conceived by intracytoplasmic sperm injection, also showed the same microdeletion. In the other families, only the men with an altered sperm analysis had a microdeletion. It is possible that in family 1, the father and brother who did not show microdeletions in this study, could have microdeletions in regions upstream or downstream of the one analyzed. The treatment with intracytoplasmic sperm injection can result in vertical transmission of microdeletions of the AZF region and can also cause the expansion of a de novo mutation. This finding reinforces the necessity of an investigation of microdeletions of the Y chromosome in individuals who are candidates for assisted reproduction, as well as genetic counciling and follow-up.