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Genetic Perspective (genetic + perspective)
Selected AbstractsGenetic perspectives on forager-farmer interaction in the Luangwa Valley of ZambiaAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2010Cesare de Filippo Abstract The transformation from a foraging way of life to a reliance on domesticated plants and animals often led to the expansion of agropastoralist populations at the expense of hunter-gatherers (HGs). In Africa, one of these expansions involved the Niger-Congo Bantu-speaking populations that started to spread southwards from Cameroon/Nigeria ,4,000 years ago, bringing agricultural technologies. Genetic studies have shown different degrees of gene flow (sometimes involving sex-biased migrations) between Bantu agriculturalists and HGs. Although these studies have covered many parts of sub-Saharan Africa, the central part (e.g. Zambia) was not yet studied, and the interactions between immigrating food-producers and local HGs are still unclear. Archeological evidence from the Luangwa Valley of Zambia suggests a long period of coexistence (,1,700 years) of early food-producers and HGs. To investigate if this apparent coexistence was accompanied by genetic admixture, we analyzed the mtDNA control region, Y chromosomal unique event polymorphisms, and 12 associated Y- short tandem repeats in two food-producing groups (Bisa and Kunda) that live today in the Luangwa Valley, and compared these data with available published data on African HGs. Our results suggest that both the Bisa and Kunda experienced at most low levels of admixture with HGs, and these levels do not differ between the maternal and paternal lineages. Coalescent simulations indicate that the genetic data best fit a demographic scenario with a long divergence (62,500 years) and little or no gene flow between the ancestors of the Bisa/Kunda and existing HGs. This scenario contrasts with the archaeological evidence for a long period of coexistence between the two different communities in the Luangwa Valley, and suggests a process of sociocultural boundary maintenance may have characterized their interaction. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Self-esteem: a behavioural genetic perspectiveEUROPEAN JOURNAL OF PERSONALITY, Issue 5 2002Michelle B. Neiss Self-esteem, the affective or evaluative appraisal of one's self, is linked with adaptive personality functioning: high self-esteem is associated with psychological health benefits (e.g. subjective well-being, absence of depression and anxiety), effective coping with illness, and satisfactory social relationships. Although several pathways have been hypothesized to effect within-family transmission of self-esteem (e.g. parenting style, family relationship patterns), we focus in this article on genetic influences. Genetic studies on both global and domain-specific self-esteem and on both level and stability of self-esteem converge in showing that (i) genetic influences on self-esteem are substantial, (ii) shared environmental influences are minimal, and (iii) non-shared environmental influences explain the largest amount of variance in self-esteem. We advocate that understanding of current issues in self-esteem research will be enriched by including behavioural genetic approaches. Copyright © 2002 John Wiley & Sons, Ltd. [source] SEXUAL ANTAGONISM AND THE EVOLUTION OF X CHROMOSOME INACTIVATIONEVOLUTION, Issue 8 2008Jan Engelstädter In most female mammals, one of the two X chromosomes is inactivated early in embryogenesis. Expression of most genes on this chromosome is shut down, and the inactive state is maintained throughout life in all somatic cells. It is generally believed that X-inactivation evolved as a means of achieving equal gene expression in males and females (dosage compensation). Following degeneration of genes on the Y chromosome, gene expression on X chromosomes in males and females is upregulated. This results in closer to optimal gene expression in males, but deleterious overexpression in females. In response, selection is proposed to favor inactivation of one of the X chromosomes in females, restoring optimal gene expression. Here, we make a first attempt at shedding light on this intricate process from a population genetic perspective, elucidating the sexually antagonistic selective forces involved. We derive conditions for the process to work and analyze evolutionary stability of the system. The implications of our results are discussed in the light of empirical findings and a recently proposed alternative hypothesis for the evolution of X-inactivation. [source] A CENTENNIAL CELEBRATION FOR QUANTITATIVE GENETICSEVOLUTION, Issue 5 2007Derek A. Roff Quantitative genetics is at or is fast approaching its centennial. In this perspective I consider five current issues pertinent to the application of quantitative genetics to evolutionary theory. First, I discuss the utility of a quantitative genetic perspective in describing genetic variation at two very different levels of resolution, (1) in natural, free-ranging populations and (2) to describe variation at the level of DNA transcription. Whereas quantitative genetics can serve as a very useful descriptor of genetic variation, its greater usefulness is in predicting evolutionary change, particularly when used in the first instance (wild populations). Second, I review the contributions of Quantitative trait loci (QLT) analysis in determining the number of loci and distribution of their genetic effects, the possible importance of identifying specific genes, and the ability of the multivariate breeder's equation to predict the results of bivariate selection experiments. QLT analyses appear to indicate that genetic effects are skewed, that at least 20 loci are generally involved, with an unknown number of alleles, and that a few loci have major effects. However, epistatic effects are common, which means that such loci might not have population-wide major effects: this question waits upon (QTL) analyses conducted on more than a few inbred lines. Third, I examine the importance of research into the action of specific genes on traits. Although great progress has been made in identifying specific genes contributing to trait variation, the high level of gene interactions underlying quantitative traits makes it unlikely that in the near future we will have mechanistic models for such traits, or that these would have greater predictive power than quantitative genetic models. In the fourth section I present evidence that the results of bivariate selection experiments when selection is antagonistic to the genetic covariance are frequently not well predicted by the multivariate breeder's equation. Bivariate experiments that combine both selection and functional analyses are urgently needed. Finally, I discuss the importance of gaining more insight, both theoretical and empirical, on the evolution of the G and P matrices. [source] Investigating intellectual disability: A genetic perspectiveJOURNAL OF PAEDIATRICS AND CHILD HEALTH, Issue 7 2003NK Poplawski Abstract: Intellectual disability (ID) is a common paediatric problem. Investigation focused on determining the aetiology of ID is warranted because a specific diagnosis may assist in prognostication, recurrence risk counselling, and identification of therapeutic and educational interventions. Three groups of screening investigations can be justified on the basis of expert opinion, common sense and the small body of published evidence-based medicine. First, investigations where current evidence justifies routine use in the investigation of ID; second, investigations which should be considered in all children with ID, although there is insufficient current evidence to support routine use; and finally, investigations which currently have an unclear role in children with ID and should be restricted to specific clinical situations unless further evidence suggesting otherwise emerges. There is a great need for systematic evaluation of the diagnostic yield of investigation templates based on this proposed stratification of investigations. [source] Range expansions in the flightless longhorn cactus beetles, Moneilema gigas and Moneilema armatum, in response to Pleistocene climate changesMOLECULAR ECOLOGY, Issue 4 2005CHRISTOPHER IRWIN SMITH Abstract Pollen cores and plant and animal fossils suggest that global climate changes at the end of the last glacial period caused range expansions in organisms indigenous to the North American desert regions, but this suggestion has rarely been investigated from a population genetic perspective. In order to investigate the impact of Pleistocene climate changes and glacial/interglacial cycling on the distribution and population structure of animals in North American desert communities, biogeographical patterns in the flightless, warm-desert cactus beetles, Moneilema gigas and Moneilema armatum, were examined using mitochondrial DNA (mtDNA) sequence data from the cytochrome oxidase I (COI) gene. Gene tree relationships between haplotypes were inferred using parsimony, maximum-likelihood, and Bayesian analysis. Nested clade analysis and coalescent modelling using the programs mdiv and fluctuate were used to identify demographically independent populations, and to test the hypothesis that Pleistocene climate changes caused recent range expansions in these species. A sign test was used to evaluate the probability of observing concerted population growth across multiple, independent populations. The phylogeographical and nested clade analyses reveal a history of northward expansion in both of these species, as well as a history of past range fragmentation, followed by expansion from refugia. The coalescent analyses provide highly significant evidence for independent range expansions from multiple refugia, but also identify biogeographical patterns that predate the most recent glacial period. The results indicate that widespread desert environments are more ancient than has been suggested in the past. [source] The interaction of plant genotype and herbivory decelerate leaf litter decomposition and alter nutrient dynamicsOIKOS, Issue 1 2005Jennifer A. Schweitzer We examined how plant genetic variation and a common herbivore (the leaf-galling aphid, Pemphigus betae) influenced leaf litter quality, decomposition, and nutrient dynamics in a dominant riparian tree (Populus spp.). Based on both observational studies and a herbivore exclusion experiment using trees of known genotype, we found four major patterns: 1) the quality of galled vs non-galled or gall-excluded litter significantly differed in the concentration of condensed tannins, lignin, nitrogen and phosphorus; 2) the difference in litter quality resulted in galled litter decomposing at rates 34 to 40% slower than non-galled litter; 3) plant genotype and herbivory had similar effects on the magnitude of decomposition rate constants; and 4) plant genotype mediated the herbivore effects on leaf litter quality and decomposition, as there were genotype-specific responses to herbivory independent of herbivore density. In contrast to other studies that have demonstrated accelerated ecosystem properties in response to arthropod herbivory, our findings argue that herbivore-induced secondary compounds decelerated ecosystem properties though their "after-life" effects on litter quality. Furthermore, these data are among the first to suggest that genotype-specific responses to herbivores can have a major impact on decomposition and nutrient flux, which likely has important consequences for the spatial distribution of nutrients at the landscape level. Due to the magnitude of these effects, we contend that it is important to incorporate a genetic perspective into ecosystem studies. [source] Genetics of human iris colour and patternsPIGMENT CELL & MELANOMA RESEARCH, Issue 5 2009Richard A. Sturm Summary The presence of melanin pigment within the iris is responsible for the visual impression of human eye colouration with complex patterns also evident in this tissue, including Fuchs' crypts, nevi, Wolfflin nodules and contraction furrows. The genetic basis underlying the determination and inheritance of these traits has been the subject of debate and research from the very beginning of quantitative trait studies in humans. Although segregation of blue-brown eye colour has been described using a simple Mendelian dominant-recessive gene model this is too simplistic, and a new molecular genetic perspective is needed to fully understand the biological complexities of this process as a polygenic trait. Nevertheless, it has been estimated that 74% of the variance in human eye colour can be explained by one interval on chromosome 15 that contains the OCA2 gene. Fine mapping of this region has identified a single base change rs12913832 T/C within intron 86 of the upstream HERC2 locus that explains almost all of this association with blue-brown eye colour. A model is presented whereby this SNP, serving as a target site for the SWI/SNF family member HLTF, acts as part of a highly evolutionary conserved regulatory element required for OCA2 gene activation through chromatin remodelling. Major candidate genes possibly effecting iris patterns are also discussed, including MITF and PAX6. [source] The genetic structure of populations from Haiti and Jamaica reflect divergent demographic historiesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Tanya M. Simms Abstract The West Indies represent an amalgamation of African, European and in some cases, East Asian sources, but the contributions from each ethnic group remain relatively unexplored from a genetic perspective. In the present study, we report, for the first time, allelic frequency data across the complete set of 15 autosomal STR loci for general collections from Haiti and Jamaica, which were subsequently used to examine the genetic diversity present in each island population. Our results indicate that although both Haiti and Jamaica display genetic affinities with the continental African collections, a stronger African signal is detected in Haiti than in Jamaica. Although only minimal contributions from non-African sources were observed in Haiti, Jamaica displays genetic input from both European and East Asian sources, an admixture profile similar to other New World collections of African descent analyzed in this report. The divergent genetic signatures present in these populations allude to the different migratory events of Africans, Europeans, and East Asians into the New World. Am J Phys Anthropol 2010. © 2009 Wiley-Liss, Inc. [source] Characterization of microsatellite loci in Spartina species (Poaceae)MOLECULAR ECOLOGY RESOURCES, Issue 1 2004Michael J. Blum Abstract The cordgrasses in the genus Spartina have become model organisms for studying biological invasions from both ecological and genetic perspectives. Here we characterize 11 disomic loci in Spartina alterniflora that show promise for population studies and for studying hybridization events between S. alterniflora and S. foliosa. Comparisons among invasive and native S. alterniflora populations showed that levels of allelic variation are lower in invasive populations. In addition, nearly all loci that amplified in S. foliosa populations and in a swarm of S. alterniflora×foliosa hybrids were polymorphic. We also found that several loci amplified successfully in other Spartina species. [source] Molecular genetic perspectives on the Indian social structureAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 3 2010B. Mohan Reddy For historical reasons, the Indian subcontinent is endowed with enormous ethnic, cultural, and genetic heterogeneity of its people. In the process of understanding the dynamics and sociocultural complexity of Indian society, anthropologists have come up with a number of hypotheses involving certain social/cultural processes that may modulate evolutionary processes. In this article, we outline some of those hypotheses and present molecular genetic evidences, both published and unpublished, to demonstrate the effects of those social/cultural processes. Am. J. Hum. Biol. 2010. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||||||||