Population structure and admixture in Cerro Largo, Uruguay, based on blood markers and mitochondrial DNA polymorphisms.

Recent studies of the Uruguayan population revealed different amounts of Amerindian and African genetic contributions. Our previous analysis of Afro-Uruguayans from the capital city of the Department of Cerro Largo showed a high proportion of African genes, and the effects of directional mating involving Amerindian women. In this paper, we extended the analysis to a sample of more than 100 individuals representing a random sample of the population of the whole Department. Based on 18 autosomal markers and one X-linked marker, we estimated 82% European, 8% Amerindian, and 10% African contributions to their ancestry, while from seven mitochondrial DNA site-specific polymorphic markers and sequences of hypervariable segment I, we determined 49% European, 30% Amerindian, and 21% African maternal contributions. Directional matings between Amerindian women and European men were detected, but differences involving Africans were not significant. Data about the specific origins of maternal lineages were also provided, and placed in a historical context.

Association between reproductive traits and four microsatellites in Brangus-Ibagé cattle

The aim of the present study was to verify associations between reproductive efficiency and four microsatellite markers located in synteny with genes involved in the regulation of reproductive mechanisms. A sample of 107 females from a Brangus Ibagé population (5/8 Aberdeen Angus x 3/8 Nelore) was characterized for ETH225 (D9S1) and MM12E6 (D9S20) microsatellites, mapped on chromosome 9, and HEL5 (D21S15) and AFZ1 (D21S37) on chromosome 21. Associations between the genetic markers and reproductive efficiency were determined by one-way analysis of variance using calving interval (CI), live weight at calving (LWC), live weight at first calving (LW1C) and live weight at second calving (LW2C) as dependent variables. The genotypes were classified according to allele size into homozygous for long alleles, homozygous for short alleles and heterozygous. A longer CI was observed for individuals homozygous for long alleles at the HEL5 locus compared with the others (p = 0.022). For the AFZ1 locus, an inverse correlation between allele size and calving interval was observed (p = 0.022), suggesting that homozygosity for long alleles at this microsatellite could be advantageous. Analysis of the combined effect of favorable genotypes at HEL5 and AFZ1 indicated that animals with unfavorable genotypes (homozygous for long alleles at HEL5 and homozygous for short alleles at AFZ1) presented a significantly longer CI (p = 0.003) when compared to the other genotypes. The ETH225 and MM12E6 systems did not present any association with CI. None of the systems studied showed any significant association with LWC, LW1C or LW2C.

Biochemical polymorphisms and genetic relationships in rodents of the genera Oryzomys and Oligoryzomys (Sigmodontinae) from Brazil.

An electrophoretic analysis of 12 allozyme systems (14 loci, 40 alleles) was performed in the rodent genera Oryzomys and Oligoryzomys, in order to determine the levels of genetic variability within and among populations and species. One hundred and fifty-five individuals from 16 populations of Oryzomys russatus, Or. angouya, Oligoryzomys flavescens, and O1. nigripes species were trapped in nine Brazilian localities. Genetic divergence among populations, as well as the interpopulational gene diversity, was higher in Oryzomys than in Oligoryzomys. The dendrogram of the phenetic relationships among the 16 populations of these four species displays three clusters: the first one joins the O1. flavescens populations with those of O1. nigripes; the second groups the populations of Or. russatus, and the last assembles the populations of Or. angouya. The genetic parameters analyzed reveal that the species belonging to the genus Oryzomys are genetically more structured than those of Oligoryzomys, the latter presenting lower levels of intrademe genetic differentiation (G(ST)')

Polymorphisms of CYP1a1, CYP2e1, GSTM1, GSTT1, and TP53 genes in Amerindians.

Polymorphisms at the TP53, cytochrome P-450 (CYP), and glutathione S-transferase (GST) genes are related to cancer susceptibility and present high diversity in allele frequencies among ethnic groups. This study concerns the CYP2E1, GSTM1, and GSTT1 polymorphisms in seven Amerindian populations (Xavante, Guarani, Aché, Wai Wai, Zoró, Surui, and Gavião). Polymorphic sites at CYP1A1 and TP53 were also studied in the Aché and Guarani tribes and compared with previous results about these systems already obtained in the other populations. The CYP2E1*5B haplotype showed, respectively, the highest and the lowest frequencies already observed in human groups. High frequencies of CYP1A1*2A and CYP1A1*2C alleles and mostly low values of GSTM1*0/*0 and GSTT1*0/*0 genotypes were observed. These data may be interpreted as being due to genetic drift or selection for these high-frequency CYP1A1 alleles and against GST null genotypes during America's colonization. Intrapopulation diversity varied from 0.19 (Guarani) to 0.38 (Surui), and 90% of the total diversity was due to the variability within populations. The relationships between these Amerindians and with other ethnic groups were evaluated based on D(A) distances and the neighbor-joining method. Low correlation was observed between genetic relationships and geographic distances or linguistic groups. In the TP53 comparison with other ethnic groups, Amerindians clustered together and then joined Chinese populations. The cluster analysis seems to indicate that the Aché tribe might descend from a Gê group that could have first colonized that Paraguayan region, but had also assimilated some amount of the Guarani gene pool, maybe through intertribal admixture.

High frequency of CYP1A1*2C allele in Brazilian populations.

The genetic variability of the CYP1A1 I462V polymorphism (CYP1A1*2C) was investigated in four Brazilian populations: three groups of African descent and one group of European descent. The CYP1A1 polymorphism was analyzed by two different procedures, first by the allele-specific polymerase chain reaction (PCR) method and then by the PCR-restricted fragment length polymorphism (PCR-RFLP) method before digestion with BsrDI. The frequency of CYP1A1 *2C was 11% in Brazilians of European descent, a frequency that is slightly higher but not statistically different from that observed in European populations. In Brazilians of African ancestry this value was very high (12% to 15%). This allele was not observed in the only two African populations investigated thus far. By themselves, the two factors of interethnic admixture (with populations of European descent and/or Amerindian populations) and genetic drift cannot explain the high values observed here. Our findings suggest that the CYP1A1 *2C allele may possibly be present in Africa, but restricted to some ethnic groups not yet investigated. Environmental factors in South America might also have acted as selective factors increasing the CYP1A1 *2C gene frequency. Our data also suggest that the CYP1A1 *2C allele might possibly have originated in Africa.

Unequal contributions of male and female gene pools from parental populations in the African descendants of the city of Melo, Uruguay.

In admixed populations, genetic contributions from males and females of specific parental populations can be of different proportions due to past directional mating during the process of genetic admixture. In this research paper, we provide evidence of such male- and female-specific differential admixture components of African, European, and American Indian origin in an admixed population from the city of Melo, in the northeastern region of Uruguay. From data on 11 autosomal markers from a sample of 41 individuals of mixed African descent, we estimated 47% African, 38% European, and 15% Amerindian contributions. In contrast, 6 mtDNA site-specific polymorphic markers showed that the mtDNA genome of these individuals was 52% African, 19% European, and 29% Amerindian, while from 3 Y-specific polymorphic sites, we estimated 30% African, 64% European, and 6% Amerindian contributions. We argue that this heterogeneity of admixture estimates results from disproportionate unions of European males with African and American Indian females from which this mixed African population was formed. Also, we argue that the asymmetry of the admixture estimates from the three sets of markers (autosomal, mtDNA, and Y-linked) is a result of the changes in the direction of mating during the history of the population. Implications of such evidence of directional mating are discussed, indicating the need of further demographic data for a quantitative assessment of the impact of directional mating on genetic structure of admixed populations.

African-derived South American populations: A history of symmetrical and asymmetrical matings according to sex revealed by bi- and uni-parental genetic markers.

Estimates of African, European, and Amerindian contributions to the gene pool of 11 predominantly African-derived South American populations were obtained using five autosomal and one Y chromosome hypervariable loci, as well as mitochondrial DNA (sequences of the first hypervariable segment of the control region, plus two restriction sites and the presence or absence of the CoII/tRNA(Lys) intergenic 9-bp deletion). The three latter characteristics are reported here for the first time for 42 individuals living in three Brazilian populations. Thirty-eight sequences were identified in these persons; 17 (45%) could be classified as being of African, 4 (11%) of Amerindian, and 2 (5%) of European origin. Evidence for asymmetrical matings in relation to sex and ethnic group was obtained for nine of the 11 populations. The most consistent finding was the introduction of European genes through males, but the results differ in the several communities, indicating the importance of local factors in such interactions. Am. J. Hum. Biol. 11:551-563, 1999. Copyright 1999 Wiley-Liss, Inc.

Genetic similarity and mate selection in Brazil

Mating patterns in humans may be affected by many variables. Previous findings, in paternity tests, of a higher average blood group genetic similarity for nonexcluded a compared to excluded or randomly paired individuals prompted the present studt, to verify if these results could be confirmed. A total of 769 couples was considered, the comparisons being made in relation to 14 loci which are expressed on blood. Excluded and nonexcluded, real couples and random pairs showed minimal differences in degree of genetic similarity. Humans choose their mates prefenrially but, as far these results indicate, independently of the genetic systems tested.

Electrophoretic protein polymorphisms in Kaingang and Guarani Indians of Southern Brazil.

A total of 337 Kaingang and Guarani Indians from two localities were studied in relation to 18 protein genetic loci. In one of the localities, members of these two groups live side by side but show little genetic similarity, emphasizing the influence of cultural factors in the mating behavior of human groups. Integrating the present results with previous ones, it was verified that the genetic relationships among six Kaingang populations do not follow the pattern expected from their geographical distribution. Comparisons made with three other Ge˜-speaking tribes indicate that the Kaingang did not separate well from them. Most (96%) of the variability in the six polymorphic systems considered occur at the intrapopulational level. Am. J. Hum. Biol. 9:505-512, 1997. © 1997 Wiley-Liss, Inc.

Is the waardemburg I syndrome gene located on chromosome

Estudos envolvendo o locus da síndrome de Waardenburg I e dois outros localizados no cromossomo 9 (sistema ABO e adenilato quinase-1) foram realizados em duas grandes famílias nordestinas. Os resultados relativos ao sistema ABO näo estäo de acordo com investigaçöes prévias, desde que näo säo sugestivos de ligaçäo

ESD, ACP and GLO frequencies in southern Brazil, with a noton heterozygosity levels

Os polimorfismos genéticos da fosfatase ácida, esterase D e glioxalase I foram investigadas em uma amostra de 363 indivíduos adultos brancos habitantes do Estado do Rio Grande do Sul. As freqüências gênicas observadas foram: ACP*A: 0,27; ACP*C: 0,03; ESD*2: 0,13; GLO*1: 0,42. Um alelo raro (ESD*3) foi encontrado em um indivíduo e seu filho. Utilizando-se dados deste e de estudos prévios calculou-se, para a populaçäo de Porto Alegre, o grau de heterozigosidade médio para respectivamente 13 e 20 sistemas eletroforéticos. Os níveis observados säo da mesma ordem de magnitude dos encontrados na América do Norte, apesar do grau mais elevado de mistura racial observado entre brasileiros

Mobility, blood genetic traits and race mixture in the Amazonian population of Oriximiná

Duzentos e seis indivíduos foram estudados, de maneira variável, com relaçäo a 16 sistemas genéticos que se expressam no sangue, informaçäo concomitante tendo sido obtida quanto à migraçäo individual, distâncias e genitor-prole, e índices de exogamia. Este grupo pode ser caracterizado como tendo mobilidade moderada, com um aumento no número de indivíduos nascidos localmente, mas também migraçäo aumentada daqueles nascidos fora de Oriximiná e agora vivendo lá, com o tempo. Com algumas exceçöes, as freqüências observadas para essas varoáveis säo similares às obtidas em outra populaçäo amazônica (Parintins). Diferenças genéticas com relaçäo a outros grupos do norte näo säo marcantes, estando principalmente confinadas aos valores de ABO*O, ESD*2 e RH*D. A prevalência obtida para este último marcador (33%) é a maior encontrada até agora na regiäo. De interesse especial, devido à sua raridade, foi a detecçäo de PGM2*11, ACP*R e ALB*Maku. O grau estimado de mistura acumulada encontrado em Oriximiná (57% Branco, 15% Negro e 28% Indígena) é similar àqueles obtidos em Manaus e Belém, mas total ou parcialmente diferente daqueles de Trombetas, Parintins e Coari. Estes estudos devem ser ampliados para a delineaçäo do perfil principal e da variabilidade genética a ser ampliados para a delineaçäo do perfl principal e da variabilidade genética a ser esperada em comunidades amazônicas

Isolate breakdown in Amazonia: the blacks of the Trombetas river

Um total de 201 indivíduos, descendentes de escravos africanos que fugiram e formaram um comunidade independente às margens dos rios Trombetas e Cuminá, foi estudada com relaçäo a 16 sistemas genéticos (dois grupos sangüíneos, hemoglobina, oito sistemas eritrocitários e cinco proteínas séricas). Dezesseis (59 por cento) dos 27 marcadores genéticos estudados apresentaram freqüências que säo típicas de populaçöes com ancestralidade africana e alguma mistura. A presença de HB*S, CA2*2, ACP*R, GD*A, GD*A- e HP*2M também indicou um conjunto gênico em grande parte africano. A estimativa quantitativa da mistura, usando 11 dos sistemas que apresentaram menos heterogeneidade, forneceu as seguintes percentagens, quanto aos componentes raciais: 62 por cento de negro, 11 por cento de indígena e 27 por cento de branco. Estimativas prévias de miscigenaçäo africana em populaçöes da regiäo amazônica resultaram em números muito menores (13 por cento a 24 por cento). Conclui-se que esta comunidade ainda mantém muito das suas características ancestrais, apesar do processo de mistura racial que está ocorrendo lá e praticamente em todo Brasil

Demography, genetics, and race admixture in Aracaju, Brazil

Foi estudado um total de 660 indivíduos com relaçäo a 13 sistemas genéticos que se expressam no sangue, tendo sido também obtida informaçäo quanto a três medidas de mobilidade populacional: migraçäo individual, e distâncias marital e genitor-prole. Esta populaçäo pode ser caracterizada como sendo de baixa mobilidade, 85% ou mais das pessoas estudadas tendo migrado menos do que 200 km. As variantes raras observadas entre elas foram: um tipo possivelmente novo de haptoglobina, denominado provisoriamente Hp Aracaju, Cp Porto Alegre, Cp New Haven, PGD Natal e ACP R. Foram desenvolvidos estudos especiais para definir os subtipos de Hp 2-1M. Os locais de origem dessas e outras variantes, considerando duas geraçöes, localizam-se em um eixo norte-sul no território de Sergipe, focos especiais ocorrendo na Costa e na regiäo próxima ao rio Säo Francisco. O genoma da amostra como um todo pode ser considerado como típico de uma populaçäo no nordeste brasileiro, ocorrendo diferenças em indivíduos com classificaçöes raciais diferentes. O grau de mistura acumulado foi estimado como sendo 62% Branco, 34% Negro e 4% Indígena

Heterozygote detection in two hyperphenylaninemia types: classic phenylketonuria and dihydrobiopterin biosynthesis deficiency

Controles normais (N=41) e heterozigotos comprovados para dois tipos de hiperfenilalaninemia (HP), fenilcetonúria clássica (HP I, N=8) e deficiência de síntese de dihidrobiopterina (HP V, N = 6), foram estudados quanto aos níveis séricos de fenilalanina (P) e tirosina (T), medidos por fluorometria. Foram observados os seguintes valores para P e T, respectivamente: controles, 79,4 + ou - 15,8 e 86,6 + ou - 19,0; HP I, 158,5 + ou - 18,8 e 96,7 + ou - 25,7; HP V, 148,3 + ou - 28,8 e 85,5 + ou - 27,7. A relaçäo p2/T e a funçäo discriminante usando simultaneamente P e T foram os parâmetros que melhor distinguiram controles dos dois tipos de heterozigotos. Näo foi possível separar heterozigotos para HP I daqueles para HP V por nenhum desses parâmetros