Inbreeding and PKU allele frequency: Estimating by microsatellite approaches.

UNLABELLED: Estimates of allele frequencies for recessive diseases are generally based on the frequency of affected individuals (q(2)). However, these estimates can be strongly biased due to inbreeding in the population. OBJECTIVES: The purpose of this study was to gain a better understanding of how inbreeding in the Minas Gerais State population affects phenylketonuria (PKU) incidence in the state and to determine the inbreeding coefficient based on microsatellites. METHODS: Inbreeding coefficients of samples of 104 controls and 76 patients with PKU were estimated through a microsatellite approach. Besides, the amount and distribution of genetic variation within and among patients with PKU and control samples were characterized. RESULTS: No genetic differentiation was observed between the samples. However, the Fis value found for samples of patients with PKU (0.042) was almost 15 times higher than that found among controls (0.003). When corrected by the inbreeding coefficient found among the controls, the PKU allele frequency decreased to 0.0057. CONCLUSIONS: The results enables us to infer that at least 35% of the PKU recessive homozygotes from the Minas Gerais population could be due to consanguineous marriages and suggest that microsatellites can be an useful approach to estimate inbreeding coefficients.

Brief communication: Admixture analysis with forensic microsatellites in Minas Gerais, Brazil: the ongoing evolution of the capital and of an African-derived community.

We report the estimated allele frequencies for 13 and 14 microsatellite loci in two populations of Minas Gerais, Brazil as follows: Belo Horizonte (the capital) and Marinhos (an African-derived community). Analysis of the African, Amerindian, and European genetic contributions to both populations, together with historical information, revealed distinct differences between the two populations. Estimates for Belo Horizonte revealed a higher-European (66%) than African (32%) contribution, and a minimal Amerindian contribution. These results are consistent with the peopling of the city mainly by people from the Minas Gerais hinterland, a people highly admixed but with more European ancestry. Estimates for Marinhos confirmed the high-African component of the population. However, a temporal analysis of two datasets-CURRENT (representing the population living in Marinhos today) and ORIGINAL (representing families, who have lived in Marinhos since the onset of the 20th century),-identified a diminishing of the population's African ancestry from 92% in the ORIGINAL group to 67% in the CURRENT group. This change is here interpreted as a consequence of the growing migration into the village of people with more European ancestry and subsequent admixture with the local population.