The aim of this study is to estimate the gene admixture in the population of Buenos Aires City from samples of blood donors, which come from a public health centre (Hospital de Clínicas). These studies were performed on 218 unrelated people, who donated blood during the year 2002. Eight erythrocyte genetic systems and GM/KM allotypes were analysed. A survey to obtain information about place of birth, present residence and genealogical data of the donors was performed. The gene frequencies were determined using a method of maximum likelihood. The genetic admixture was calculated through the ADMIX program (trihibride). The Amerindian and African contributions were 15.8% and 4.3% respectively. These data were compared with those obtained in a previous study performed in a private centre (Hospital Italiano de Buenos Aires) and significant differences were observed, except in the KM system. The results obtained are in concordance with the demographic and historic information of Buenos Aires City.

Este estudio tiene como objetivo estimar la mezcla génica en la población de la Ciudad de Buenos Aires, a partir de muestras de dadores de sangre provenientes de un centro público de salud (Hospital de Clínicas). Los estudios se realizaron sobre 218 personas no emparentadas que donaron su sangre durante el año 2002. Se analizaron 8 sistemas genéticos eritrocitarios y los alotipos GM/KM. Se realizó una encuesta con la finalidad de obtener información sobre lugar de nacimiento, residencia actual y datos genealógicos de los dadores. Las frecuencias génicas se determinaron empleando métodos de máxima verosimilitud. Para calcular la mezcla génica se aplicó el programa ADMIX (trihíbrido). Se registró un 15.8% de aporte indígena (AI) y 4.3% de africano (AA). Estos datos se compararon con un estudio previo realizado en un centro privado (Hospital Italiano de Buenos Aires), no observándose diferencias significativas salvo en el sistema Km. Los resultados obtenidos se corresponden con la información histórica y demográfica de la ciudad de Buenos Aires.

The allelic variability of four dinucleotide microsatellites located in the HLA region (MOGc, D6S265, MIB, and TNFa) was analyzed in 67 individuals representing three Amerindian populations of the Argentine Gran Chaco: Toba, Wichi and Chorote. Genomic DNA was prepared from peripheral blood and DNA was extracted using the standard phenol-chloroform procedure. Alleles were identified by PCR, using an end-labelled reverse oligonucleotide primer (fluorescent 6 - Fam labeling). Despite the low number of samples studied, a high level of gene diversity was observed in each population and for each locus. Moreover, the mean number of alleles was 7.7, 5.3, 10.0, and 7.0 at loci MOGc, D6S265, MIB and TNFa, respectively. Differentiation tests between pairs of populations showed a clear differentiation between the Wichi and the other two groups. However, the proportion of the total genetic variability that is due to differences among populations, estimated by the Gst' index, was relatively low (6%). Almost all the genetic variation occurred at the intra-population level (96%). The high intra-populational genetic variation suggests the existence of an intensive gene flow among the Gran Chaco tribes. Historical information seems to confirm this result.