397 research outputs found
Proportioning whole-genome single-nucleotide-polymorphism diversity for the identification of geographic population structure and genetic ancestry
The identification of geographic population structure and genetic ancestry
on the basis of a minimal set of genetic markers is desirable for a wide
range of applications in medical and forensic sciences. However, the
absence of sharp discontinuities in the neutral genetic diversity among
human populations implies that, in practice, a large number of neutral
markers will be required to identify the genetic ancestry of one
individual. We showed that it is possible to reduce the amount of markers
required for detecting continental population structure to only 10
single-nucleotide polymorphisms (SNPs), by applying a newly developed
ascertainment algorithm to Affymetrix GeneChip Mapping 10K SNP array data
that we obtained from samples of globally dispersed human individuals (the
Y Chromosome Consortium panel). Furthermore, this set of SNPs was able to
recover the genetic ancestry of individuals from all four continents
represented in the original data set when applied to an independent, much
larger, worldwide population data set (Centre d'Etude du Polymorphisme
Humain-Human Genome Diversity Project Cell Line Panel). Finally, we
provide evidence that the unusual patterns of genetic variation we
observed at the respective genomic regions surrounding the five most
informative SNPs is in agreement with local positive selection being the
explanation for the striking SNP allele-frequency differences we found
between continental groups of human populations
The effect of the apolipoprotein E phenotype on plasma lipids is not influenced by environmental variability: results of a Dutch twin study
We tested the influence of the apolipoprotein E (apoE) polymorphism on the intrapair differences in the levels of plasma cholesterol, plasma triglycerides, low density lipoprotein-cholesterol, apoB and apoE in monozygotic (MZ) twins, and estimated whether or not there was a interaction between the apoE polymorphism and environmental factors. In 65 MZ twin pairs, the intrapair differences in the measured lipoprotein parameters were similar in the different apoE phenotype classes. This indicates that the effect of the apoE polymorphism is not influenced by environmental variability between the MZ pair members and accordingly identifies the APOE gene as a "level" gene. © 1993 Springer-Verlag
Imaging dielectric relaxation in nanostructured polymers by frequency modulation electrostatic force microscopy
We have developed a method for imaging the temperature-frequency dependence of the dynamics of nanostructured polymer films with spatial resolution. This method provides images with dielectric compositional contrast well decoupled from topography. Using frequency-modulation electrostatic-force-microscopy, we probe the local frequency-dependent (0.1–100 Hz) dielectric response through measurement of the amplitude and phase of the force gradient in response to an oscillating applied electric field. When the phase is imaged at fixed frequency, it reveals the spatial variation in dielectric losses, i.e., the spatial variation in molecular/dipolar dynamics, with 40 nm lateral resolution. This is demonstrated by using as a model system; a phase separated polystyrene/polyvinyl-acetate (PVAc) blend. We show that nanoscale dynamic domains of PVAc are clearly identifiable in phase images as those which light-up in a band of temperature, reflecting the variations in the molecular/dipolar dynamics approaching the glass transition temperature of PVAc
A powerful and rapid approach to human genome scanning in small quantities of genomic DNA
Dense maps of short-tandem-repeat polymorphisms (STRPs) have allowed genome-wide searches for genes involved in a great variety of diseases with genetic influences, including common complex diseases. Generally for this purpose, marker sets with a 10 cM spacing are genotyped in hundreds of individuals. We have performed power simulations to estimate the maximum possible intermarker distance that still allows for sufficient power. In this paper we further report on modifications of previously published protocols, resulting in a powerful screening set containing 229 STRPs with an average spacing of 18·3 cM. A complete genome scan using our protocol requires only 80 multiplex PCR reactions which are all carried out using one set of conditions and which do not contain overlapping marker allele sizes. The multiplex PCR reactions are grouped by sets of chromosomes, which enables on-line statistical analysis of a set of chromosomes, as sets of chromosomes are being genotyped. A genome scan following this modified protocol can be performed using a maximum amount of 2.5 μg of genomic DNA per individual, isolated from either blood or from mouth swabs.link_to_subscribed_fulltex
Deciduous Teeth as an Alternative DNA Source for Postmortem Genetic Testing
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Short hypervariable microhaplotypes: A novel set of very short high discriminating power loci without stutter artefacts
Molecular Technology and Informatics for Personalised Medicine and Healt
FDSTools: A software package for analysis of massively parallel sequencing data with the ability to recognise and correct STR stutter and other PCR or sequencing noise
Molecular Technology and Informatics for Personalised Medicine and Healt
Phylogeographic Patterns in Africa and High Resolution Delineation of Genetic Clades in the Lion (Panthera leo)
Comparative phylogeography of African savannah mammals shows a congruent pattern in which populations in West/Central Africa are distinct from populations in East/Southern Africa. However, for the lion, all African populations are currently classified as a single subspecies (Panthera leo leo), while the only remaining population in Asia is considered to be distinct (Panthera leo persica). This distinction is disputed both by morphological and genetic data. In this study we introduce the lion as a model for African phylogeography. Analyses of mtDNA sequences reveal six supported clades and a strongly supported ancestral dichotomy with northern populations (West Africa, Central Africa, North Africa/Asia) on one branch, and southern populations (North East Africa, East/Southern Africa and South West Africa) on the other. We review taxonomies and phylogenies of other large savannah mammals, illustrating that similar clades are found in other species. The described phylogeographic pattern is considered in relation to large scale environmental changes in Africa over the past 300,000 years, attributable to climate. Refugial areas, predicted by climate envelope models, further confirm the observed pattern. We support the revision of current lion taxonomy, as recognition of a northern and a southern subspecies is more parsimonious with the evolutionary history of the lion.Netherlands Organization for Scientific Research (NWO) (project no. 820.01.002)
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