P. Brito

Analysis of paternal lineages in Brazilian and African populations

The present-day Brazilian population is a consequence of the admixture of various peoples of very different origins, namely, Amerindians, Europeans and Africans. The proportion of each genetic contribution is known to be very heterogeneous throughout the country. The aim of the present study was to compare the male lineages present in two distinct Brazilian populations, as well as to evaluate the African contribution to their male genetic substrate. Thus, two Brazilian population samples from Manaus (State of Amazon) and Ribeirão Preto (State of São Paulo) and three African samples from Guinea Bissau, Angola and Mozambique were typed for a set of nine Y chromosome specific STRs. The data were compared with those from African, Amerindian and European populations. By using Y-STR haplotype information, low genetic distances were found between the Manaus and Ribeirão Preto populations, as well as between these and others from Iberia. Likewise, no significant distances were observed between any of the African samples from Angola, Mozambique and Guinea Bissau. Highly significant Rst values were found between both Brazilian samples and all the African and Amerindian populations. The absence of a significant Sub-Saharan African male component resulting from the slave trade, and the low frequency in Amerindian ancestry Y-lineages in the Manaus and Ribeirão Preto population samples are in accordance with the accentuated gender asymmetry in admixture processes that has been systematically reported in colonial South American populations.

Genetic anomaly and clinical history and its implication in paternity analysis

This paper describes a paternity case investigation that became a maternity investigation, in which the mother of two dizygotic male twins referred having received a bone marrow transplant, donated by her sister, seven years before, due to a sickle cell disease. The study of 17 STRs with different commercial kits revealed two maternal inconsistencies with one child and one inconsistency with the other. The alleged father was excluded as the biological father without genetic information of the mother. After receiving our report, the court decided to investigate the maternity relative to the children. Supplementary studies with more STRs and with other mother biological tissues revealed distinct genetic profiles in blood, epithelial cells and hair roots. The profile obtained from the hair roots was consistent with being the mother of her children. This case shows the importance of accurate information about the medical condition of all the involved persons, along with the collection of hair roots, especially when one of the participants has had a bone marrow transplant.