Phylogenetic evidence for multiple independent duplication events at the DYS19 locus

Duplication events at Y chromosome STR loci have been repeatedly described in human populations. DYS19 is probably the best known example and it exhibits duplicate state in individuals from all continents. Despite the large amount of available data, evolutionary relationship between DYS19 duplication-bearing chromosomes has not been so far investigated. We address the genealogical correlation among such chromosomes by analysing newly identified DYS19 duplicated Y chromosomes by SNP genotyping and microsatellite-based network analysis. SNP and network analysis show that DYS19 duplicated Y chromosomes associate with different Y chromosome lineages. These results indicate that DYS19 duplication occurred more than once during human evolution.     

The paternal genetic structure of Jingpo and Dai in southwest China

Yunnan province harbours substantial genetic, cultural and linguistic diversity, with the largest number of Aborigines in China, but the relationship among these Aborigines remains enigmatic. This study genotyped 45 Y chromosomal single nucleotide polymorphisms (SNPs) of 500 males from two aboriginal cross-border populations, Jingpo and Dai, from Dehong, Yunnan. It is reported that Haplogroup O2a2b1a1-M117 is the dominant lineage in both Jingpo and Dai. The Jingpo people show affinity with Tibeto-Burman speaking populations with a relatively high frequency of Haplogroup D-M174, and the Dai people are generally genetically similar with Tai-Kadai speaking populations with high frequencies of Haplogroup O1a-M119 and O1b1a1a-M95, which is consistent with their language classification.     

Ongoing tissue changes in an experimentally mummified human leg

Artificial mummification has been used since antiquity and is best known from ancient Egypt. Despite ancient Egyptian mummies being studied for several decades, the mummification techniques of that time are not well understood. Modern mummification experiments involving animal and human tissues have contributed additional insights relevant to a broad field of research. In the current study, we present follow-up results of an experiment on artificial mummification, which began in 2009. A human leg was artificially mummified and monitored for almost a year with histological, molecular, and radiological techniques. Since then, it has remained in a dry, natron salt blend for 9 years. The current analyses show further progression of dehydration and tissue alterations, as well as DNA degradation, suggesting an ongoing process. Our results add new insights into the mechanisms of tissue mummification. Taking into account that the process is still ongoing, further research is required, including a re-evaluation of the human leg in the future.     

Stigma matters: HIV and HIV risk perception among men who have sex with men in Serbia; a qualitative study

As a social determinant of health, stigma is a major barrier to health care access, illness management and completing the treatment. It is attributed both to HIV as a health condition and to the populations at risk of being infected with it. In Serbia, HIV is associated with men who have sex with men (MSM), with a noticeable stigma towards them. Drawing upon a qualitative cross-sectional study, conducted in three Serbian cities, we explore the MSM’s perception of HIV in the context of that social stigma. Using a respondent-driven sampling approach, 62 targeted MSM respondents participated in focus groups discussions and in-depth interviews. We found that the participants’ understandings of the HIV infection, risks and prevention are shaped by stigma. Those MSM who resisted stigma relativised the HIV risk, associating it with the general population and HIV-positive MSMs, believing that HIV, perceived as a chronical illness, was unjustly related to MSM. As one of the main preventive measures, serosorting was based on alleged HIV-positive statuses of potential sexual partners. HIV-negative participants described perceiving HIV-positive MSM as the ones responsible for spreading the virus, since they were concealing their positive status. As a response to stigma, MSM tended to challenge the HIV discourse, shifting it away from MSM onto the general (male) population and HIV positive MSM. Our analysis suggests that stigma resistance may make MSM more susceptible to taking risks. HIV prevention programmes should take the social context of MSM into account and target MSM-related stigma.     

生物与文化:流行病学与人类学跨学科合作

生物学是流行病学研究的重要基础,基于此,心理、社会和文化等因素也将影响或作用于疾病和健康。以往的“生物医学模式”向“生物-心理-社会医学模式”转变,在此过程中“文化”因素尚未被充分重视。因此重视人类学中“文化”研究,以之与流行病学的生物基础相结合,可成为人类学与流行病学跨学科合作的角度之一。     

Paternity exclusion power: Comparative behaviour of autosomal and X-chromosomal markers in standard and deficient cases with inbreeding

In paternity testing the informativeness of genetic markers is traditionally measured through the probability of finding, in randomly chosen individuals, inconsistencies with parent to child Mendelian rules of transmission. This statistic, called power of exclusion (PE), paternal exclusion chance or probability, can be defined for duos (mother not typed) or trios (random false fathers are matched against mother/child pairs) and performed both for autosomal and X-chromosomal markers (restricted to paternity testing involving daughters). PE is an a priori statistic, in the sense of not depending on the individual's genetic data of a case, being dependent however on the estimates of genetic markers allele (or haplotype) frequencies.We have studied the behaviour of this statistic in situations where the randomness assumption is not met, because either (a) the alleged – and false – father is related to the true one, or (b) there is a non-negligible level of background relatedness in the population.For the first case, we derived general (autosomal and X-chromosomal) PE formulas for duos and trios for any genealogy linking alleged father and child, highlighting that the PE of each marker only depends on a single kinship parameter associated with their pedigree. In this case we also estimate a lower bound for the number of extra markers needed to be analysed to achieve the same global power as for unrelated individuals. In the second situation, we demonstrate that for realistic values of the coancestry coefficient the decrease in PE due to population inbreeding is very moderate even when duos are analysed.In this work, beyond the aforementioned issues, we also discuss the suitability of assuming the pedigree father–daughter for calculating the X-PE, since X-markers are not the tool of choice in laboratorial routine when the alleged father is available for testing. Indeed, X-markers are particularly useful in situations where the alleged father is not available for testing but experts are able to type the mother or a daughter of his. Such increase of power is due to the paternal genealogies: half- and full-sisters, and grandmother–granddaughter, having a non-null X-PE even when only duos are analysed in contrast to what happens for autosomes. Algebraic expressions for these cases are also presented.