Selection on the Human Bitter Taste Gene, TAS2R16, inEurasian Populations

Bitter taste is one of the most important senses alerting humans to noxious foods. In gatherer communities, sensitivity to bitterness is presumably advantageous because of various noxious plants. TAS2R16 is the gene coding the taste receptor molecules for some of the most common toxins in plants. A previous study of this gene indicated selection has increased the frequency of a derived allele in this gene that arose before the human expansion out of Africa. We have applied a different methodology for detecting selection, the Long Range Haplotype (LRH) analysis, to TAS2R16 in a larger sampling of populations from around the world. The haplotype with the derived alleles at both the functional polymorphism and a polymorphism in the regulatory region of TAS2R16 showed evidence for recent positive selection in most of the Eurasian populations, though the highest selection signal occurs in Mbuti Pygmies, an African hunter-gatherer group. In Eurasia, only populations of Mesopotamia and the southeast coast of China have no signals of selection. The evidence of recent selection found in most Eurasian populations differs from the geographic pattern seen in the earlier study of selection. One can speculate that the difference may result from a gathering lifestyle extending into the most recent 10,000 yrs and the need to recognize newly encountered bitter natural toxins as populations expanded into new environments and the biota changes with the ending of the most recent ice age. Alternatively, the promoter region variant may be a marker for altered function beyond what the derived amino acid allele conferred

Quantum chaos in a Bose-Hubbard dimer with modulated tunnelling

In the large-$N$, classical limit, the Bose-Hubbard dimer undergoes a transition to chaos when its tunnelling rate is modulated in time. We use exact and approximate numerical simulations to determine the features of the dynamically evolving state that are correlated with the presence of chaos in the classical limit. We propose the statistical distance between initially similar number distributions as a reliable measure to distinguish regular from chaotic behaviour in the quantum dynamics. Besides being experimentally accessible, number distributions can be efficiently reconstructed numerically from binned phase-space trajectories in a truncated Wigner approximation. Although the evolving Wigner function becomes very irregular in the chaotic regions, the truncated Wigner method is nevertheless able to capture accurately the beyond mean-field dynamics.Comment: 10 pages, 10 figure

First contemporary case of human infection with Cryptococcus gattii in Puget Sound: Evidence for spread of the Vancouver Island outbreak

We report a case of cryptococcosis due to C. gattii which appears to have been acquired in the Puget Sound region, Washington State. Genotyping confirmed identity to the predominant Vancouver Island genotype. This is the first documented case of human disease by the major Vancouver Island emergence strain acquired within the United States

Borrelia burgdorferi and the causative agent of human granulocytic ehrlichiosis in deer ticks, Delaware.

During the 1998 hunting season in Delaware, 1,480 ticks were collected from 252 white- tailed deer; 98% were Ixodes scapularis, a significant increase from the 85% reported in 1988. Ticks were tested for Borrelia burgdorferi and the causative agent of human granulocytic ehrlichiosis. Infection rates remained stable in New Castle and Kent counties, but increased from <1% to 8% in sussex county

ALFRED: an allele frequency resource for research and teaching

ALFRED (http://alfred.med.yale.edu) is a free, web accessible, curated compilation of allele frequency data on DNA sequence polymorphisms in anthropologically defined human populations. Currently, ALFRED has allele frequency tables on over 663 400 polymorphic sites; 170 of them have frequency tables for more than 100 different population samples. In ALFRED, a population may have multiple samples with each ‘sample’ consisting of many individuals on which an allele frequency is based. There are 3566 population samples from 710 different populations with allele frequency tables on at least one polymorphism. Fifty of those population samples have allele frequency data for over 650 000 polymorphisms. Records also have active links to relevant resources (dbSNP, PharmGKB, OMIM, Ethnologue, etc.). The flexible search options and data display and download capabilities available through the web interface allow easy access to the large quantity of high-quality data in ALFRED

Mongolians in the Genetic Landscape of Central Asia: Exploring the Genetic Relations among Mongolians and Other World Populations

Genetic data on North Central Asian populations are underrepresented in the literature, especially autosomal markers. In the present study we use 812 single nucleotide polymorphisms that are distributed across all the human autosomes and that have been extensively studied at Yale to examine the affinities of two recently collected, samples of populations: rural and cosmopolitan Mongolians from Ulaanbaatar and nomadic, Turkic-speaking Tsaatan from Mongolia near the Siberian border. We compare these two populations to one another and to a global set of populations and discuss their relationships to New World populations. Specifically, we analyze data on 521 autosomal loci (single SNPs and multi-SNP haplotypes) studied on 57 populations representing all the major geographical regions of the world. We conclude that the North Central Asian populations we study are genetically distinct from all other populations in our study and may be close to the ancestral lineage leading to the New World populations

Manipulation of subsurface carbon nanoparticles in Bi2Sr2CaCu2O8+δ using a scanning tunneling microscope

We present evidence that subsurface carbon nanoparticles in Bi2Sr2CaCu2O8+δ can be manipulated with nanometer precision using a scanning tunneling microscope. High-resolution images indicate that most of the carbon particles remain subsurface after transport observable as a local increase in height as the particle pushes up on the surface. Tunneling spectra in the vicinity of these protrusions exhibit semiconducting characteristics with a band gap of approximately 1.8 eV, indicating that the incorporation of carbon locally alters the electronic properties near the surface