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Mutation Effects (mutation + effects)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

THE FITNESS EFFECT OF MUTATIONS ACROSS ENVIRONMENTS: A SURVEY IN LIGHT OF FITNESS LANDSCAPE MODELS

EVOLUTION, Issue 12 2006
Guillaume Martin
Abstract The fitness effects of mutations on a given genotype are rarely constant across environments to which this genotype is more or less adapted, that is, between more or less stressful conditions. This can have important implications, especially on the evolution of ecological specialization. Stress is thought to increase the variance of mutations' fitness effects, their average, or the number of expressed mutations. Although empirical evidence is available for these three mechanisms, their relative magnitude is poorly understood. In this paper, we propose a simple approach to discriminate between these mechanisms, using a survey of empirical measures of mutation effects in contrasted environments. This survey, across various species and environments, shows that stress mainly increases the variance of mutations effects on fitness, with a much more limited impact on their average effect or on the number of expressed mutations. This pattern is consistent with a simple model in which fitness is a Gaussian function of phenotypes around an environmentally determined optimum. These results suggest that a simple, mathematically tractable landscape model may not be quantitatively as unrealistic as previously suggested. They also suggest that mutation parameter estimates may be strongly biased when measured in stressful environments. [source]

Genetic Toxicology of Dental Composite Resin Extracts in Somatic Cells In Vivo

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 1 2010
Guilherme Anziliero Arossi
Homologous mitotic recombination, point and chromosomal mutation effects were determined in somatic proliferative cells of Drosophila melanogaster exposed to aqueous extracts of the clinically used composites. Reproducible increases in clone mutant spot frequencies induced by diluted extract of Fill Magic Flow were observed. These increments were exclusively associated to the induction of homologous recombination , a genetic phenomenon involved in the loss of heterozygosis. The other eight composite resins and the random extract had no statistically significant effect on total spot frequencies , suggesting that they are non-genotoxic in the somatic mutation and recombination test assay, which agrees with the applications they have in dentistry. These findings , supported by numerous studies showing a positive correlation between carcinogenicity in man and genotoxicity in the Drosophila wing spot test , point to the potential risks some composite resins pose to the health of patients and dentistry personnel. [source]

Lipoprotein Mutation Accelerates Substrate Permeability-Limited Toluene Dioxygenase-Catalyzed Reaction

BIOTECHNOLOGY PROGRESS, Issue 3 2005
Ye Ni
One of the major problems in whole-cell biocatalysis is its low reaction rate. The underlying cause is the substrate permeation barrier presented by cell envelopes. The present research investigates mutation effects of the Braunapos;s lipoprotein, the most abundant outer membrane structural protein in Escherichia coli, on toluene dioxyengase (TDO)-catalyzed reaction. Dramatic enhancement of the reaction rate, an increase of up to 6-fold, was observed with the mutant for all three small, hydrophobic substrates tested (toluene, ethylbenzene, and 2-indanone). The increase was observed over a wide range of substrate concentrations (0.1,5 mM). The mutant exhibited a normal growth rate and expressed the recombinant multicomponent enzyme as well as the isogenic parent strain. Taken together, the lipoprotein mutant expressing TDO is a much better whole-cell catalyst for the oxidation reaction. The beneficial effect of the lipoprotein mutation may be general for a broad range of substrates and enzyme systems as the mutation affects the global integrity of the cell membrane. A comparison of the mutation effect with a common permeabilizing procedure, the EDTA treatment, further illustrates the clear advantages of using genetic modification in cellular membrane engineering for improved whole-cell catalysts. [source]

THE FITNESS EFFECT OF MUTATIONS ACROSS ENVIRONMENTS: A SURVEY IN LIGHT OF FITNESS LANDSCAPE MODELS

EVOLUTION, Issue 12 2006
Guillaume Martin
Abstract The fitness effects of mutations on a given genotype are rarely constant across environments to which this genotype is more or less adapted, that is, between more or less stressful conditions. This can have important implications, especially on the evolution of ecological specialization. Stress is thought to increase the variance of mutations' fitness effects, their average, or the number of expressed mutations. Although empirical evidence is available for these three mechanisms, their relative magnitude is poorly understood. In this paper, we propose a simple approach to discriminate between these mechanisms, using a survey of empirical measures of mutation effects in contrasted environments. This survey, across various species and environments, shows that stress mainly increases the variance of mutations effects on fitness, with a much more limited impact on their average effect or on the number of expressed mutations. This pattern is consistent with a simple model in which fitness is a Gaussian function of phenotypes around an environmentally determined optimum. These results suggest that a simple, mathematically tractable landscape model may not be quantitatively as unrealistic as previously suggested. They also suggest that mutation parameter estimates may be strongly biased when measured in stressful environments. [source]