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Results for “GENOTYPE BY ENVIRONMENT”

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At least 19 recordsLinked to original sources
PubMed1981

Genetical variation for enzyme activity in a population of Drosophila melanogaster. VII. Genotype-environment interaction for alcohol dehydrogenase (ADH) activity.

Genotype-environment interaction was detected for ADH activity amongst a set of 18 highly inbred lines of Drosophila melanogaster which had been extracted from the laboratory population, "Texas". The genotype-environment interaction for ADH activity was not wholly associated with genotype-environment interaction for body weight or total protein level. Detailed analyses of the responses of the individual inbred lines in ADH activity in relation to the environmental index, ej and following the procedure of Jinks and Pooni (1979), showed substantial diversity in the form of response. Lines homozygous for the AdhF allele were more environmentally sensitive than AdhS/S lines. Amongst the 16 AdhS/S lines, models of linear, quadratic or two intersecting-straight-lines were used to illustrate the varied responses of genotypes to the environment. The heterogeneity in the response characteristics of the inbred lines was attributed to variations in the conditions of culture media normally present within populations and laboratories. Moreover the non-linear responses shown by some lines to the environment are consistent with a model of genotype-environment interaction for ADH activity mediated by varied genotype-specific sensitivities to different environmental factors.

Alcohol Oxidoreductases↗
PubMed1994

Additive-multiplicative approximation of genotype-environment interaction.

A model of genotype-environment interaction in quantitative traits is considered. The model represents an expansion of the traditional additive (first degree polynomial) approximation of genotypic and environmental effects to a second degree polynomial incorporating a multiplicative term besides the additive terms. An experimental evaluation of the model is suggested and applied to a trait in Drosophila melanogaster. The environmental variance of a genotype in the model is shown to be a function of the genotypic value: it is a convex parabola. The broad sense heritability in a population depends not only on the genotypic and environmental variances, but also on the position of the genotypic mean in the population relative to the minimum of the parabola. It is demonstrated, using the model, that G x E interaction may cause a substantial non-linearity in offspring-parent regression and a reversed response to directional selection. It is also shown that directional selection may be accompanied by an increase in the heritability.

Animals↗
PubMed1999

Quantitative trait loci affecting survival and fertility-related traits in Caenorhabditis elegans show genotype-environment interactions, pleiotropy and epistasis.

We have identified, using composite interval mapping, quantitative trait loci (QTL) affecting a variety of life history traits (LHTs) in the nematode Caenorhabditis elegans. Using recombinant inbred strains assayed on the surface of agar plates, we found QTL for survival, early fertility, age of onset of sexual maturity, and population growth rate. There was no overall correlation between survival on solid media and previous measures of survival in liquid media. Of the four survival QTL found in these two environments, two have genotype-environment interactions (GEIs). Epistatic interactions between markers were detected for four traits. A multiple regression approach was used to determine which single markers and epistatic interactions best explained the phenotypic variance for each trait. The amount of phenotypic variance accounted for by genetic effects ranged from 13% (for internal hatching) to 46% (for population growth). Epistatic effects accounted for 9-11% of the phenotypic variance for three traits. Two regions containing QTL that affected more than one fertility-related trait were found. This study serves as an example of the power of QTL mapping for dissecting the genetic architecture of a suite of LHTs and indicates the potential importance of environment and GEIs in the evolution of this architecture.

Animals↗
PubMed1999

Method to detect genotype-environment interactions for quantitative trait loci in association studies.

Khoury et al. (Am J Hum Genet 1988;42:89-95 and Am J Epidemiol 1993;137:1241-50) presented an epidemiologic approach to examine genotype-environment interaction in situations where the disease is either present or absent. In this article, the author extends the approach of Khoury et al. to quantitative outcome variables. This extension is relevant for diseases that are extremes on a continuum or when continuous risk factors are studied. To account for a possible admixture of subgroups in the sample, tests for genotype-environment interaction are discussed for designs with parents as controls as well as without parents as controls. Assuming two environmental conditions, the author demonstrates how the power of these tests can be calculated and used to estimate the sample sizes needed to detect genotype-environment interaction in a variety of conditions. In addition, he analyzes simulated data to demonstrate the detection of different mechanisms of genotype-environment interaction and to study the effectiveness of this approach to identify the correct mechanism. Finally, extensions to multiple environmental conditions and designs with multiple subjects per family are discussed.

Analysis of Variance↗
PubMed1987

The genetic structure of natural populations of Drosophila melanogaster. XX. Comparison of genotype-environment interaction in viability between a northern and a southern population.

In order to examine the operation of diversifying selection as the maintenance mechanism of excessive additive genetic variance for viability in southern populations in comparison with northern populations of Drosophila melanogaster, two sets of experiments were conducted using second chromosomes extracted from the Ogasawara population (a southern population in Japan) and from the Aomori population (a northern population in Japan). Chromosomal homozygote and heterozygote viabilities were estimated in eight kinds of artificially produced breeding environments. The main findings in the present investigation are as follows: (1) Significant genotype-environment interaction was observed using chromosomes extracted from the Ogasawara population. Indeed, the estimate of the genotype-environment interaction variance for heterozygotes was significantly larger than that of the genotypic variance. On the other hand, when chromosomes sampled from the Aomori population were examined, that interaction variance was significant only for homozygotes and its value was no more than one quarter of that for the chromosomes from the Ogasawara population. (2) The average genetic correlation between any two viabilities of the same lines estimated in the eight kinds of breeding environments for the chromosomes sampled from the Ogasawara population was smaller than that for the chromosomes from the Aomori population both in homozygotes and in heterozygotes, especially in the latter. (3) The stability of heterozygotes over homozygotes against fluctuations of environmental conditions was seen in the chromosomes from the Ogasawara population, but not from the Aomori population. (4) From the excessive genotype-environment interaction variance compared with the genotypic variance in heterozygotes, it was suggested for the chromosomes from the Ogasawara population that the reversal of viability order between homozygotes took place in some environments at the locus level. On the basis of these findings, it is strongly suggested that diversifying selection is operating in a southern population of D. melanogaster on some of the viability polygenes which are probably located outside the structural loci, and the excessive additive genetic variance of viability in southern populations is maintained by this type of selection.

Alleles↗
PubMed1976

The significance for breeding of linear regression analysis of genotype-environment interactions.

Methods of regression analysis of genotype-environment interaction are considered in relation to existing theory dealing with the relative efficiencies of selection for general or specific adaptation to the environment, and the choice of environments for assessment. The two alternative models is involving regression on to environmental effects (model 2) or genotypic effects (model 3) are equivalent when regression lines are concurrent, but are shown to be mutually exclusive when concurrence is absent...

Crosses, Genetic↗
PubMed1999

Genotype-environment interaction in human obesity.

The data reviewed in this paper reveal that individual differences in the response to alterations in energy balance induced by diet or exercise are ubiquitous. These differences are observed in a variety of obesity-related phenotypes, including body weight, body fatness, and abdominal visceral fat. Although little is known about the causes of the heterogeneity in responsiveness to dietary habits or to regular exercise, the evidence accumulated so far suggests that genetic factors may play an important role in determining the response of body mass and body fat stores to chronic alterations in energy balance. It is likely that genetic variation at several genes contributes to this heterogeneity of responses and thus to the susceptibility to obesity. Research on the genetic and molecular basis of gene-environment interactions has become a major area of investigation. One can, therefore, anticipate that major advances will occur in the coming years with respect to the identification of the genetic and molecular causes of the susceptibility to the most common diseases, including obesity.

Adult↗
PubMed1992

More about the multiplicative model for the analysis of genotype-environment interaction.

In this paper various multiplicative models that are often used to analyse genotype-environment interaction are described and some of the statistical relationships between them are explored. It is shown that principal-component analysis can be seen as a natural generalization of the joint regression analysis. A set of maize data is used to exemplify these statistical models.

Environment↗
PubMed2004

Genotype-environment interactions of spontaneous mutations for vegetative fitness in the human pathogenic fungus Cryptococcus neoformans.

Spontaneous mutation is the ultimate source of all genetic variation. By interacting with environmental factors, genetic variation determines the phenotype and fitness of individuals in natural populations. However, except in a few model organisms, relatively little is known about the patterns of genotype-environment interactions of spontaneous mutations. Here I examine the rates of spontaneous mutation and the patterns of genotype-environment interaction of mutations affecting vegetative growth in the human fungal pathogen Cryptococcus neoformans. Eight mutation accumulation (MA) lines were established from a single clone on the nutrient-rich medium YEPD for each of two temperatures, 25 degrees and 37 degrees. Cells from generations 100, 200, 400, and 600 for each of the 16 MA lines were stored and assayed for vegetative growth rates under each of four conditions: (i) 25 degrees on SD (a synthetic dextrose minimal medium); (ii) 25 degrees on YEPD; (iii) 37 degrees on SD; and (iv) 37 degrees on YEPD. Both MA conditions and assay environments for vegetative growth showed significant influence on the estimates of genomic mutation rates, average effect per mutation, and mutational heritability. Significant genotype-environment interactions were detected among the newly accumulated spontaneous mutations. Overall, clones from MA lines maintained at 37 degrees showed less decline in vegetative fitness than those maintained at 25 degrees. The result suggests that a high-temperature environment might be very important for the maintenance of the ability to grow at a high temperature. Results from comparisons between clinical and environmental samples of C. neoformans were consistent with laboratory experimental population analyses. This study calls into question our long-standing view that warm-blooded mammals were only occasional and accidental hosts of this human fungal pathogen.

Cryptococcus neoformans↗
PubMed2004

Interactive effects of genotype, environment, and ontogeny on resistance of cucumber (Cucumis sativus) to the generalist herbivore, Spodoptera exigua.

Host-plant genotype, environment, and ontogeny all play a role in determining plant resistance to herbivory, yet little is known about the nature of the interactions among these factors. We investigated resistance of cucumber plants Cucumis sativus to the generalist herbivore Spodoptera exigua in a manipulative experiment involving three factors. In particular, we tested the effects of bitter (cucurbitacins present) vs. sweet (cucurbitacins absent) plants (genotype), with or without previous herbivory (environment), and cotyledons vs. true leaves (ontogeny). Contrary to our expectations, S. exigua growth was 54% higher on bitter plants than on sweet plants; growth was 63% higher, however, on undamaged plants compared to damaged plants, and 59% higher on true leaves compared to cotyledons. Moreover, all two-way interaction terms between genotype, environment, and ontogeny were significant. For example, S. exigua performance was higher on bitter than on sweet plants; however, this effect was strongly influenced by whether the tissue consumed was a cotyledon or true leaf and also whether it had been previously damaged. An examination of leaf nutritional chemistry revealed that some of our results could be explained by genotypic, environmental, and ontogenic differences in foliar nitrogen content. In contrast, the cucurbitacin content of plants did not appear to affect caterpillar growth. Our results provide evidence for the importance of interactions between genotype, environment, and ontogeny in determining herbivory and illustrate the value of manipulative experiments in revealing the complexities of these interactions.

Adaptation, Physiological↗