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Mutation Events (mutation + event)
Selected AbstractsThe kdr mutation occurs in the Mopti form of Anopheles gambiaes.s. through introgressionINSECT MOLECULAR BIOLOGY, Issue 5 2000M. Weill Abstract Anopheles gambiaes.s. is a complex of sibling taxa characterized by various paracentric inversions. In west and central Africa, where several taxa are sympatric, a kdr mutation responsible for pyrethroid resistance has been described in only one (the S taxon), suggesting an absence of gene flow between them. Following a thorough sampling, we have found a kdr mutation in another taxon (M). To establish whether this mutation is the same event or not, the large intron upstream of the kdr mutation was sequenced to find polymorphic sites in susceptible/resistant and M/S mosquitoes. The low genetic diversity found in this DNA region indicates that a local genetic sweep has recently occurred. However, some polymorphic sites were found, and it is therefore concluded that the kdr mutation in the M taxon is not an independent mutation event, and is best explained by an introgression from the S taxon. These results are discussed within the context of possible gene flow between members of An. gambiae s.s. taxa, and with the possible spread of the kdr mutation in other closely related malaria vectors of the An. gambiae complex. [source] Ancestral Inference in Population Genetics Models with Selection (with Discussion)AUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 4 2003Matthew Stephens Summary A new algorithm is presented for exact simulation from the conditional distribution of the genealogical history of a sample, given the composition of the sample, for population genetics models with general diploid selection. The method applies to the usual diffusion approximation of evolution at a single locus, in a randomly mating population of constant size, for mutation models in which the distribution of the type of a mutant does not depend on the type of the progenitor allele; this includes any model with only two alleles. The new method is applied to ancestral inference for the two-allele case, both with genic selection and heterozygote advantage and disadvantage, where one of the alleles is assumed to have resulted from a unique mutation event. The paper describes how the method could be used for inference when data are also available at neutral markers linked to the locus under selection. It also informally describes and constructs the non-neutral Fleming,Viot measure-valued diffusion. [source] Variation in mitochondrial DNA control region haplotypes in populations of the bank vole, Clethrionomys glareolus, living in the Chernobyl environment, UkraineENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2006Jeffrey K. Wickliffe Abstract Bank vole, Clethrionomys glareolus, specimens have been annually sampled from the radioactive Chernobyl, Ukraine, environment and nonradioactive reference sites since 1997. Exposed voles continually exhibit increased mitochondrial DNA hap-lotype (h) and nucleotide diversity (ND), observed in the hypervariable control region (1997,1999). Increased maternal mutation rates, source,sink relationships, or both are proposed as hypotheses for these differences. Samples from additional years (2000 and 2001) have been incorporated into this temporal study. To evaluate the hypothesis that an increased mutation rate is associated with increased h, DNA sequences were examined in a phylogenetic context for novel substitutions not observed in haplotypes from bank voles from outside Ukraine or in other species of Clethrionomys. Such novel substitutions might result from in situ mutation events and, if largely restricted to samples from radioactive environments, support an increased maternal mutation rate in these areas. The only unique substitution meeting this criterion was found in an uncontaminated reference site. All other substitutions are found in other haplotypes of the bank vole or in other species. Increased maternal mutation rates do not appear to explain trends in h and ND observed in northern Ukraine. Studies examining ecological dynamics will clarify the reasons behind, and significance of, increased levels of h in contaminated areas. [source] Determination of the genetic status of cleavage-stage human embryos by microsatellite marker analysis following multiple displacement amplificationPRENATAL DIAGNOSIS, Issue 3 2007Pamela J. Renwick Abstract Objectives To analyse genotype information from cleavage-stage human embryos and assess the chromosomal status and feasibility of performing aneuploidy screening by microsatellite analysis. Methods DNA from 49 blastomeres from eight cleavage-stage human embryos was amplified using multiple displacement amplification, then tested for panels of 64 polymorphic microsatellite markers on seven different chromosomes, and for two non-polymorphic sequences on the X and Y chromosomes. Results There was an overall allele drop out (ADO) rate of 28%. Novel alleles in single cells were seen in 0.3% of amplifications, interpreted as either somatic microsatellite mutation events or ,slippage' of the MDA , 29 polymerase. Three-allele results for a single marker in a single cell were found in 0.07% of amplifications, interpreted as ,slippage' of the MDA , 29 polymerase. One apparent segmental duplication was found. Only one embryo with no normal cells was found, probably arising from the chaotic cleavage division following a triploid conception. Six embryos were mosaic, of which four had only one abnormal cell. Conclusions Abnormalities in human embryos may be present in only a single cell, leading to potentially false abnormal results at pre-implantation genetic diagnosis. ADO associated with MDA reduces the efficacy of this approach for detection of aneuploidy. Statistical analysis showed that, for ADO of 28%, seven informative markers would be required to give 95% confidence of detecting trisomic embryos. Copyright © 2007 John Wiley & Sons, Ltd. [source] Tyrosinase mutations associated with Siamese and Burmese patterns in the domestic cat (Felis catus)ANIMAL GENETICS, Issue 2 2005L. A. Lyons Summary The Siamese cat has a highly recognized coat colour phenotype that expresses pigment at the extremities of the body, such as the ears, tail and paws. This temperature-sensitive colouration causes a ,mask' on the face and the phenotype is commonly referred to as ,pointed'. Burmese is an allelic variant that is less temperature-sensitive, producing more pigment throughout the torso than Siamese. Tyrosinase (TYR) mutations have been suspected to cause these phenotypes because mutations in TYR are associated with similar phenotypes in other species. Linkage and synteny mapping in the cat has indirectly supported TYR as the causative gene for these feline phenotypes. TYR mutations associated with Siamese and Burmese phenotypes are described herein. Over 200 cats were analysed, representing 12 breeds as well as randomly bred cats. The SNP associated with the Siamese phenotype is an exon 2 G > A transition changing glycine to arginine (G302R). The SNP associated with the Burmese phenotype is an exon 1 G > T transversion changing glycine to tryptophan (G227W). The G302R mutation segregated concordantly within a pedigree of Himalayan (pointed) Persians. All cats that had ,pointed' or the Burmese coat colour phenotype were homozygous for the corresponding mutations, respectively, suggesting that these phenotypes are a result of the identified mutations or unidentified mutations that are in linkage disequilibrium. Because the same mutations were identified in different breeds with similar phenotypes, the mutations are likely to be identical by descent rather than multiple mutation events occurring at the same site. [source] | ||||||||||