Contrasting signals of positive selection in genes involved in human skin-color variation from tests based on SNP scans and resequencing.

Background: Numerous genome-wide scans conducted by genotyping previously ascertained single-nucleotide polymorphisms (SNPs) have provided candidate signatures for positive selection in various regions of the human genome, including in genes involved in pigmentation traits. However, it is unclear how well the signatures discovered by such haplotype-based test statistics can be reproduced in tests based on full resequencing data. Four genes (oculocutaneous albinism II (OCA2), tyrosinase-related protein 1 (TYRP1), dopachrome tautomerase (DCT), and KIT ligand (KITLG)) implicated in human skin-color variation, have shown evidence for positive selection in Europeans and East Asians in previous SNP-scan data.

Signatures of positive selection in genes associated with human skin pigmentation as revealed from analyses of single nucleotide polymorphisms.

Phenotypic variation between human populations in skin pigmentation correlates with latitude at the continental level. A large number of hypotheses involving genetic adaptation have been proposed to explain human variation in skin colour, but only limited genetic evidence for positive selection has been presented. To shed light on the evolutionary genetic history of human variation in skin colour we inspected 118 genes associated with skin pigmentation in the Perlegen dataset, studying single nucleotide polymorphisms (SNPs), and analyzed 55 genes in detail.

Morphological variability within Oesophagostomum bifurcum among different primate species from Ghana.

Adult Oesophagostomum bifurcum (Nematoda: Strongylida) from human and non-human primates from Ghana were compared in order to investigate the extent of morphological variability within the species. Using analysis of variance and principal component analysis, significant differences in morphological characters (such as parasite length, width, length of the oesophagus and length of spicules) were demonstrated between O. bifurcum worms from humans, the Mona, Patas or Green monkey and/or Olive baboons.

AFLP fingerprinting for the analysis of genetic diversity within Necator americanus.

In the present study, we utilised the method of AFLP to screen for genetic variation within and among individuals of the blood-feeding human hookworm Necator americanus (Nematoda) from Africa, Asia and South America. A total of 45 adult worms (i.e.

Oesophagostomum bifurcum in non-human primates is not a potential reservoir for human infection in Ghana.

In northern Togo and Ghana, human infection with the parasitic nematode Oesophagostomum bifurcum is of major health importance. Elsewhere, oesophagostomiasis is considered a zoonotic infection, non-human primates being the natural host. We examined 349 faecal samples of the olive baboon, mona monkey and black and white colobus monkey from two geographically distinct areas in Ghana, outside the region endemic for O.