Search results for "Polymorphism"
showing 10 items of 1968 documents
Multiple testing in candidate gene situations: a comparison of classical, discrete, and resampling-based procedures.
2011
In candidate gene association studies, usually several elementary hypotheses are tested simultaneously using one particular set of data. The data normally consist of partly correlated SNP information. Every SNP can be tested for association with the disease, e.g., using the Cochran-Armitage test for trend. To account for the multiplicity of the test situation, different types of multiple testing procedures have been proposed. The question arises whether procedures taking into account the discreteness of the situation show a benefit especially in case of correlated data. We empirically evaluate several different multiple testing procedures via simulation studies using simulated correlated SN…
Tailoring sparse multivariable regression techniques for prognostic single-nucleotide polymorphism signatures.
2011
When seeking prognostic information for patients, modern technologies provide a huge amount of genomic measurements as a starting point. For single-nucleotide polymorphisms (SNPs), there may be more than one million covariates that need to be simultaneously considered with respect to a clinical endpoint. Although the underlying biological problem cannot be solved on the basis of clinical cohorts of only modest size, some important SNPs might still be identified. Sparse multivariable regression techniques have recently become available for automatically identifying prognostic molecular signatures that comprise relatively few covariates and provide reasonable prediction performance. For illus…
Adaptive linear rank tests for eQTL studies
2012
Expression quantitative trait loci (eQTL) studies are performed to identify single-nucleotide polymorphisms that modify average expression values of genes, proteins, or metabolites, depending on the genotype. As expression values are often not normally distributed, statistical methods for eQTL studies should be valid and powerful in these situations. Adaptive tests are promising alternatives to standard approaches, such as the analysis of variance or the Kruskal-Wallis test. In a two-stage procedure, skewness and tail length of the distributions are estimated and used to select one of several linear rank tests. In this study, we compare two adaptive tests that were proposed in the literatur…
Polymorphism in Cs[AgZn(NCS)4].
2002
The title compound, caesium silver zinc tetrathiocyanate, crystallizes in two polymorphic forms, in space groups P2(1)/n and C2/c. Both structures form a continuous three-dimensional network. The structure in C2/c contains a delocalized Ag atom in a binuclear-like anion, where two [Ag(NCS)(4)] units (delocalized Ag as an average) share two common NCS(-) ligands.
Data from: Gray plumage color is more cryptic than brown in snowy landscapes in a resident color polymorphic bird
2020
Camouflage may promote fitness of given phenotypes in different environments. The tawny owl (Strix aluco) is a colour polymorphic species with a grey and brown morph resident in the Western Palearctic. A strong selection pressure against the brown morph during snowy and cold winters has been documented earlier but the selection mechanisms remain unresolved. Here we hypothesise that selection favors the grey morph because it is better camouflaged against predators and mobbers in snowy conditions compared to the brown one. We conducted an online citizen science experiment where volunteers were asked to locate a grey or a brown tawny owl specimen from pictures taken in snowy and snowless lands…
STRUCTURE AND PHASE TRANSITIONS IN [C(NH2)3]SbCl6 CRYSTALS
1998
Abstract The crystal structure of [C(NH2)3]SbCl6 at 298 K (monoclinic, C2/m) and 240 K (monoclinic, P21/a) has been determined. The structure consists of isolated SbCl6− anions and guanidinium cations. Differential scanning calorimetry, dilatometric and dielectric studies revealed two structural phase transitions; a first-order one at 351 K and a second-order one at 265 K. One of the two crystallographically non-equivalent anions, SbCl6−(1), disordered in the room temperature phase is postulated to contribute to the phase transition mechanism at 265 K. A ferroelastic domain structure is found below 351 K.
The role of geographic setting on the diversification process among Tephritis conura (Tephritidae) host races
2006
We address the controversy over the processes causing divergence during speciation. Host races of the fruit fly Tephritis conura attack the thistles Cirsium oleraceum and Cirsium heterophyllum. By studying the genetic divergence of T. conura in areas where host plants are sympatric, parapatric and allopatric, we assessed the contribution of geography in driving host-race divergence. We also evaluated the relative importance of genetic drift and selection in the diversification process, by analysis of the geographic distribution of genetic variation. Host races were significantly diverged at five out of 13 polymorphic allozyme loci. Variance at two loci, Hex and Pep D, was almost exclusively…
Rapid radiation of North American desert genera of the Papaveraceae: Evidence from restriction site mapping of PCR-amplified chloroplast DNA fragments
1995
Phylogenetic relationships of a group of North American desert genera of the Papaveraceae subfam. Papaveroideae and Platystemonoideae were investigated with an RFLP analysis of three PCR-amplified chloroplast genome regions. In agreement with earlier results it was found that subfam. Platystemonoideae is nested within subfam. Papaveroideae. The group under study is characterized by a large number of generic autapomorphies but only few informative synapomorphies. This is interpreted as strong evidence for a rapid radiation event caused by major climatic changes in the past. Poor phylogenetic resolution seems to reflect biological reality and not to be an experimental artifact. There is also …
One is not enough: On the effects of reference genome for the mapping and subsequent analyses of short-reads.
2020
Mapping of high-throughput sequencing (HTS) reads to a single arbitrary reference genome is a frequently used approach in microbial genomics. However, the choice of a reference may represent a source of errors that may affect subsequent analyses such as the detection of single nucleotide polymorphisms (SNPs) and phylogenetic inference. In this work, we evaluated the effect of reference choice on short-read sequence data from five clinically and epidemiologically relevant bacteria (Klebsiella pneumoniae, Legionella pneumophila, Neisseria gonorrhoeae, Pseudomonas aeruginosa and Serratia marcescens). Publicly available whole-genome assemblies encompassing the genomic diversity of these species…
Polymorphisms of genes of TGF-beta pathway and susceptibility to colorectal cancer
2012
Background: Genetic background implicated in cytokine network may have a key role in the susceptibility to colorectal cancer (CRC). The TGF-β pathway is involved in several biological processes, including cell proliferation, differentiation, migration and apoptosis. Methods: rs1800471 SNP polymorphism of TGF-ß1 rs334348 and rs334349 of TGF-βR1, rs900 of TGF-β2 and rs4522809 of TGF-β2R2 were typed in a group of 82 patients affected by sporadic CRC and in 237 age- and sex-matched healthy controls, using a competitive allele specific PCR assays (KASPar), developed by KBioscience (England). Results: No significant genetic contribution has been observed for 3 of the 5 SNPs tested. Indeed, a sign…