Case-control studies are a powerful strategy to identify candidate genes in complex diseases. In admixed populations, association studies can be affected by population stratification, leading to spurious genetic associations. Ancestry informative markers (AIMs) can be used to minimise this effect. The aim of this work was to select a set of AIMs to estimate population stratification in a Brazilian case-control study performed using a genome-wide array. A total of 345 single nucleotide polymorphism (SNP) AIMs, selected from the Cytoscan HD array and based on previously reported panels, was used to discriminate between European, African, and Amerindian populations. These SNP-AIMs were used to infer ancestry in systemic lupus erythematosus (SLE) patients (n  =  23) and in healthy subjects (n  =  110). Moderate population substructure was observed between SLE and control groups (F 0.0113). Although patients and controls have shown a major European genomic contribution, significant differences in the European (P  =  6.47 × 10 ) and African (P  =  1.14 × 10 ) ancestries were detected between the two groups. We performed a two-step validation of the 345 SNP-AIMs panel estimating the ancestral contributions using a panel of 12 AIMs and approximately 70K SNPs from the array. Evaluation of population substructure in case-control studies, avoiding spurious genetic associations, can be performed using our panel of 345 SNP-AIMs.

The mutation age and local ancestry of chromosomal segments harbouring mutations associated with autosomal recessive (AR) disorders in Brazilian admixed populations remain unknown; additionally, inbreeding levels for these affected individuals continue to be estimated based on genealogical information. Here, we calculated inbreeding levels using a runs of homozygosity approach, mutation age and local ancestry to infer the origin of each chromosomal segments containing disorder-causing mutations in KLC2, IMPA1, MED25 and WNT7A. Genotyped data were generated from 18 patients affected by AR diseases and combined to the 1000 genome project (1KGP) and Simons genome diversity project (SGDP) databases to infer local ancestry. We found a major European contribution for mutated haplotypes with recent mutation age and inbreeding values found only in Native American and Middle East individuals. These results contribute to identifying the origin of and to understanding how these diseases are maintained and spread in Brazilian and world populations.

Arqueometria é uma abordagem multidisciplinar dirigida a uma grande gama de assuntos das diferentes áreas da Arqueologia, auxiliando com respostas às suas indagações. Uma área também pouco estudada ainda é a Arqueoquímica que, dentro de seus tópicos, tem o estudo dos parâmetros diagenéticos a partir de técnicas espectroscópicas. Neste trabalho, é feita uma revisão dos conjuntos de processos que envolvem as alterações físicas, químicas, histológicas e mecânicas chamadas de diagênese. Além disso, neste mesmo trabalho, foram comparadas duas técnicas de análise: a espectroscopia Fourier transform infrared by attenuated total reflectance spectroscopy (FTIR-ATR), que analisa a interação da radiação com a matéria, com o objetivo de determinar as energias das vibrações das moléculas; e a Difração de Raios X (DRX), técnica que caracteriza a estrutura cristalina dos materiais. Ambas as técnicas foram aplicadas em um fragmento de tíbia humana evidenciado no sítio Pedra do Alexandre no Rio Grande do Norte, um fêmur bovino evidenciado no sítio Pilar em Pernambuco e um fêmur humano moderno. Os parâmetros diagenéticos foram determinados com o intuito de avaliar sua aplicação comparando ambas as técnicas no estudo da diagênese óssea. ABSTRACTArchaeometry is multidisciplinary approach addressed to a wide range of topics from different archaeological areas, supporting it with answers for its quests. One area poor studied yet is archaeochemistry that within its topics has the study of diagenetic parameters by spectroscopic techniques. This work is a review of the processes that involve the physical, chemical, histological and mechanic called diagenesis. Moreover, it was also compared two techniques of spectroscopic analysis, ATR-FTIR (Fourier transform infrared by attenuated total reflectance spectroscopy) that analyzes the interaction between radiation of the matter with the aim to determine the molecule vibrations energy; and the X-ray diffraction (XRD), technique that characterize the materials crystalline structure. Both techniques were applied in a human tibia fragment evidenced in Pedra do Alexandre archaeological site, Rio Grande do Norte state; one bovine femur from Pilar archaeological site, Pernambuco state; and one modern human femur. The diagenetic parameters were determined in order to evaluate its application comparing both techniques in the bone diagenesis study.Keywords: bones diagenesis, spectroscopy, archeology.

This paper deals with the frequency and structure of first-cousin marriages, by far the most important and frequent type of consanguineous mating in human populations. Based on the analysis of large amounts of data from the world literature and from large Brazilian samples recently collected, we suggest some explanations for the asymmetry of sexes among the parental sibs of first-cousin marriages. We suggest also a simple manner to correct the method that uses population surnames to assess the different Wright fixation indexes FIS, FST and FIT taking into account not only alternative methods of surname transmission, but also the asymmetries that are almost always observed in the distribution of sexes among the parental sibs of first-cousins.

The aim of this cross-sectional study was to investigate beliefs, attitudes and reproductive behaviours in relation to consanguinity in a population living in the backlands of north-eastern Brazil. Data were collected by face-to-face interview from 147 high school students aged 13–20 years and from 532 elderly individuals aged 60 years and over from Brejo dos Santos in the state of Paraíba in 2017. The frequency of consanguineous marriage was found to have increased over the generations, being 15.9% in the parents of the elderly participants, 17.1% in the elderly participants themselves and 20.5% in their descendants. Although 258 (50.9%) of the elderly interviewees opposed consanguineous union, 341 (65.3%) would approve of the marriage of their children with relatives. Both the young (n=108 or 78.3%) and elderly (n=398 or 80.4%) interviewees believed that consanguineous marriages were no more durable than non-consanguineous marriages (p=0.578). Additionally, 408 (82.4%) of the elderly individuals and 108 (80.6%) of the students recognized that spouses in consanguineous unions experience conflicts, just like other couples do (p=0.625). In both groups, the majority of the participants did not believe that consanguinity increased the risk of having children with disabilities. The regression of the two continuous variables ‘age’ and ‘positive attitudes score’ showed a significant correlation, suggesting that younger individuals are more susceptible to the influence of cultural factors contributing to consanguinity, such as the opinions of their parents and grandparents. The belief that consanguineous unions are more durable showed a significant difference between elderly individuals in consanguineous and non-consanguineous unions (p=0.001); the former were 2.42 more likely to believe that marriages between relatives contributes to marriage durability.