scholarly journals Regeneration of the variance of metric traits by spontaneous mutation in a Drosophila population

2010 ◽  
Vol 92 (2) ◽  
pp. 91-102 ◽  
Author(s):  
CARMEN AMADOR ◽  
AURORA GARCÍA-DORADO ◽  
DIEGO BERSABÉ ◽  
CARLOS LÓPEZ-FANJUL
Keyword(s):  
Spontaneous Mutation ◽  
Temporal Stability ◽  
Stabilizing Selection ◽  
Additive Variance ◽  
Heterozygous Condition ◽  
Bristle Number ◽  
Laboratory Populations ◽  
The Mean ◽  
Metric Traits ◽  
Recessive Effects

SummaryIn the C1 population of Drosophila melanogaster of moderate effective size (≈500), which was genetically invariant in its origin, we studied the regeneration by spontaneous mutation of the genetic variance for two metric traits [abdominal (AB) and sternopleural (ST) bristle number] and that of the concealed mutation load for viability, together with their temporal stability, using alternative selection models based on mutational parameters estimated in the C1 genetic background. During generations 381–485 of mutation accumulation (MA), the additive variances of AB and ST approached the levels observed in standing laboratory populations, fluctuating around their expected equilibrium values under neutrality or under relatively weak causal stabilizing selection. This type of selection was required to simultaneously account for the observed additive variance in our population and for those previously reported in natural and laboratory populations, indicating that most mutations affecting bristle traits would only be subjected to weak selective constraints. Although gene action for bristles was essentially additive, transient situations occurred where inbreeding resulted in a depression of the mean and an increase of the additive variance. This was ascribed to the occasional segregation of mutations of large recessive effects. On the other hand, the observed non-lethal inbreeding depression for viability must be explained by the segregation of alleles of considerable and largely recessive deleterious effects, and the corresponding load concealed in the heterozygous condition was found to be temporally stable, as expected from tighter constraints imposed by natural selection.

The action of evolutionary forces on metric traits

2011 ◽  
Vol 1 (3) ◽  
pp. 532-537
Author(s):  
C. López-Fanjul
Keyword(s):  
Genetic Variance ◽  
Natural Populations ◽  
Substantial Contribution ◽  
Additive Variance ◽  
Evolutionary Forces ◽  
Bristle Number ◽  
Laboratory Populations ◽  
Component Traits ◽  
Mean Fitness ◽  
Metric Traits

Fisher's theorem of natural selection implies that the population genetic variance of quasi-neutral traits should be mostly additive. In the case of fitness component traits, however, that variance would be characterised by a substantial contribution from non-additive loci. In parallel, Robertson's theorem states that selection will change the population mean of a trait proportionally to the magnitude of the genetic correlation between that trait and fitness, which should be weak for quasi-neutral traits or strong for the mean fitness components. Drosophila data from inbreeding and artificial selection experiments are discussed within that theoretical framework. In addition, the process of regeneration by mutation of the genetic variance of a quasi-neutral trait (abdominal bristle number) in a Drosophila population initially homozygous at all loci has been analysed. After 485 generations of mutation accumulation, the levels of additive variance found in this population closely approached those commonly observed in laboratory populations. Furthermore, these values, together with previously reported estimates for natural populations, could be jointly explained by a model assuming weak causal stabilising selection.

scholarly journals Association of single-nucleotide polymorphisms at the Delta locus with genotype by environment interaction for sensory bristle number in Drosophila melanogaster

2002 ◽  
Vol 79 (3) ◽  
pp. 211-218 ◽  
Author(s):  
GRETCHEN L. GEIGER-THORNSBERRY ◽  
TRUDY F. C. MACKAY
Keyword(s):  
Standard Deviation ◽  
Single Nucleotide Polymorphisms ◽  
Genotype By Environment Interaction ◽  
Stabilizing Selection ◽  
Environment Interaction ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Genotype By Environment ◽  
Bristle Number ◽  
The Mean

The nature of forces maintaining variation for quantitative traits can only be assessed at the level of individual genes affecting variation in the traits. Identification of single-nucleotide polymorphisms (SNPs) associated with variation in Drosophila sensory bristle number at the Delta (Dl) locus provides us with the opportunity to test a model for the maintenance of variation in bristle number by genotype by environment interaction (GEI). Under this model, genetic variation is maintained at a locus under stabilizing selection if phenotypic values of heterozygotes are more stable than homozygotes across a range of environments, and the mean allelic effect is much smaller than the standard deviation of allelic effects across environments. Homozygotes and heterozygotes for two SNPs at Dl, one affecting sternopleural and the other abdominal bristle number, were reared in five different environments. There was significant GEI for both bristle traits. Neither condition of the model was satisfied for Dl SNPs exhibiting GEI for sternopleural bristle number. Heterozygotes for the abdominal bristle number SNPs were indeed the most stable genotype for two of the three environment pairs exhibiting GEI, but the mean genotypic effect was greater than the standard deviation of effects across environments. Therefore, this mechanism of GEI seems unlikely to be responsible for maintaining the common bristle number polymorphisms at Dl.

Short-term Changes in the Variance: 1. Changes in the Additive Variance

2018 ◽  
Author(s):  
Bruce Walsh ◽  
Michael Lynch
Keyword(s):  
Linkage Disequilibrium ◽  
Assortative Mating ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Allele Frequencies ◽  
Disruptive Selection ◽  
Stabilizing Selection ◽  
Short Term ◽  
Additive Variance ◽  
The Mean

Selection changes the additive-genetic variance (and hence the response in the mean) by both changing allele frequencies and by generating correlations among alleles at different loci (linkage disequilibrium). Such selection-induced correlations can be generated even between unlinked loci, and (generally) are negative, such that alleles increasing trait values tend to become increasingly negative correlated under direction or stabilizing selection, and positively correlated under disruptive selection. Such changes in the additive-genetic variance from disequilibrium is called the Bulmer effects. For a large number of loci, the amount of change can be predicted from the Bulmer equation, the analog of the breeder's equation, but now for the change in the variance. Upon cessation of selection, any disequilibrium decays away, and the variances revert back to their additive-genic variances (the additive variance in the absence of disequilibrium). Assortative mating also generates such disequilibrium.

scholarly journals Polygenic mutation in Drosophila melanogaster: the causal relationship of bristle number to fitness.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 861-872 ◽  
Author(s):  
S V Nuzhdin ◽  
J D Fry ◽  
T F Mackay
Keyword(s):  
Drosophila Melanogaster ◽  
Artificial Selection ◽  
Random Mating ◽  
Direct Selection ◽  
Stabilizing Selection ◽  
Fitness Effects ◽  
Bristle Number ◽  
Mean Fitness ◽  
The Mean ◽  
Average Fitness

Abstract The association between sternopleural and abdominal bristle number and fitness in Drosophila melanogaster was determined for sublines of an initially highly inbred strain that were maintained by divergent artificial selection for 150 generations or by random mating for 180 generations. Replicate selection lines had more extreme bristle numbers than those that were maintained without artificial selection at the same census size for approximately the same number of generations. The average fitness, estimated by a single generation of competition against a compound autosome strain, was 0.17 for lines selected for high and low abdominal bristle numbers and 0.19 for lines selected for high and low sternopleural bristle number. The average fitness of unselected lines, 0.46, was significantly higher than that of the selection lines. The fitnesses and the relationships of bristle number to fitness in progeny of all possible crosses of high x high (H x H), high x low (H x L) and low x low (L x L) selection lines were examined to determine whether the observed intermediate optima were caused by direct stabilizing selection on bristle number or by apparent stabilizing selection mediated through deleterious pleiotropic fitness effects of mutations affecting bristle number. Although bristle number was nearly additive for progeny of H x H, H x L and L x L crosses among sternopleural bristle selection lines, their mean fitnesses were not significantly different from each other, or from the mean fitness of the unselected lines, suggesting partly or completely recessive pleiotropic fitness effects cause apparent stabilizing selection. The average fitness of the progeny of H x H abdominal bristle selection lines was not significantly different from the fitness of unselected lines, but the mean fitness of the progeny of L x L crosses was not significantly different from that of the pure low lines. This is consistent with direct selection against low but not high abdominal bristle number, but the interpretation is confounded by variation in average degree of dominance for fitness (on average recessive in the high abdominal bristle selection lines and additive in the low abdominal bristle selection lines). Neither direct stabilizing selection nor pleiotropy, therefore, can account for all the observations.

Whole-Genome Effects of Ethyl Methanesulfonate-Induced Mutation on Nine Quantitative Traits in Outbred Drosophila melanogaster

Genetics ◽  
2001 ◽  
Vol 157 (3) ◽  
pp. 1257-1265 ◽  
Author(s):  
Hsiao-Pei Yang ◽  
Ana Y Tanikawa ◽  
Wayne A Van Voorhies ◽  
Joana C Silva ◽  
Alexey S Kondrashov
Keyword(s):  
Drosophila Melanogaster ◽  
Quantitative Traits ◽  
Spontaneous Mutation ◽  
Developmental Time ◽  
Ethyl Methanesulfonate ◽  
Induced Mutations ◽  
Mean Values ◽  
Eye Color ◽  
Recessive Mutations ◽  
The Mean

Abstract We induced mutations in Drosophila melanogaster males by treating them with 21.2 mm ethyl methanesulfonate (EMS). Nine quantitative traits (developmental time, viability, fecundity, longevity, metabolic rate, motility, body weight, and abdominal and sternopleural bristle numbers) were measured in outbred heterozygous F3 (viability) or F2 (all other traits) offspring from the treated males. The mean values of the first four traits, which are all directly related to the life history, were substantially affected by EMS mutagenesis: the developmental time increased while viability, fecundity, and longevity declined. In contrast, the mean values of the other five traits were not significantly affected. Rates of recessive X-linked lethals and of recessive mutations at several loci affecting eye color imply that our EMS treatment was equivalent to ∼100 generations of spontaneous mutation. If so, our data imply that one generation of spontaneous mutation increases the developmental time by 0.09% at 20° and by 0.04% at 25°, and reduces viability under harsh conditions, fecundity, and longevity by 1.35, 0.21, and 0.08%, respectively. Comparison of flies with none, one, and two grandfathers (or greatgrandfathers, in the case of viability) treated with EMS did not reveal any significant epistasis among the induced mutations.

Biological Aspects of a High Socio-Economic Group

1970 ◽  
Vol 2 (1) ◽  
pp. 1-16 ◽  
Author(s):  
John B. Gibson
Keyword(s):  
Social Class ◽  
Social Stratification ◽  
Educational Opportunity ◽  
Population Sample ◽  
Stabilizing Selection ◽  
Class Differences ◽  
Social Scale ◽  
The Social ◽  
Biological Aspects ◽  
The Mean

Data are presented on the social backgrounds and IQs of a sample of scientists, their male sibs and their fathers. The range of IQ in the scientists is similar to the range of scores expected of the higher 25% of a representative general population sample.The IQs of the scientists showed a positive correlation with social class. Differences in IQ between the scientists and their fathers in each social class are related to the distance the scientists have moved up the social scale. In the twenty-two families in which the IQs of the father and two male sibs are known the upwardly mobile sibs tend to have higher IQs than the non-mobile or downwardly mobile sibs.In Class II there is evidence that stabilizing selection operates on IQ to maintain the mean IQ level. The effect on social stratification of such selection, together with increased educational opportunity, is discussed.

scholarly journals Evolutionary dynamics of neutral phenotypes under DNA substitution models

2020 ◽  
Author(s):  
Shadi Zabad ◽  
Alan M Moses
Keyword(s):  
Dna Sequences ◽  
Evolutionary Dynamics ◽  
Gc Content ◽  
Stabilizing Selection ◽  
Restoring Force ◽  
Dna Substitution ◽  
Long Term Trends ◽  
The Mean ◽  
Molecular Phenotypes

AbstractWe study the evolution of quantitative molecular traits in the absence of selection. Using a simple theory based on Felsenstein’s 1981 DNA substitution model, we predict a linear restoring force on the mean of an additive phenotype. Remarkably, the mean dynamics are independent of the effect sizes and genotype and are similar to the widely-used OU model for stabilizing selection. We confirm the predictions empirically using additive molecular phenotypes calculated from ancestral reconstructions of putatively unconstrained DNA sequences in primate genomes. We show that the OU model is favoured by inference software even when applied to GC content of unconstrained sequences or simulations of DNA evolution. We predict and confirm empirically that the dynamics of the variance are more complicated than those predicted by the OU model, and show that our results for the restoring force of mutation hold even for non-additive phenotypes, such as number of transcription factor binding sites, longest encoded peptide and folding propensity of the encoded peptide. Our results have implications for efforts to infer selection based on quantitative phenotype dynamics as well as to understand long-term trends in evolution of quantitative molecular traits.

scholarly journals Preprint: Psychometric properties of startle and corrugator response in NPU, Affective Picture Viewing, and Resting State tasks

2018 ◽  
Author(s):  
Jesse T Kaye ◽  
Daniel E. Bradford ◽  
John Joseph Curtin
Keyword(s):  
Psychometric Properties ◽  
Resting State ◽  
Startle Response ◽  
Comprehensive Evaluation ◽  
Temporal Stability ◽  
Frequency Domains ◽  
Two Measures ◽  
The Mean ◽  
Picture Viewing ◽  
Startle Potentiation

The current study provides a comprehensive evaluation of critical psychometric properties of commonly used psychophysiology laboratory tasks/measures within the NIMH RDoC. Participants (N = 128) completed the No Shock, Predictable Shock, Unpredictable Shock (NPU) task, Affective Picture Viewing task, and Resting State task at two study visits separated by one week. We examined potentiation/modulation scores in NPU (predictable or unpredictable shock vs. no shock) and Affective Picture Viewing tasks (pleasant or unpleasant vs. neutral pictures) for startle and corrugator responses with two commonly used quantification methods. We quantified startle potentiation/modulation scores with raw and standardized responses. We quantified corrugator potentiation/modulation in the time and frequency domains. We quantified general startle reactivity in the Resting State Task as the mean raw startle response during the task. For these three tasks, two measures, and two quantification methods we evaluated effect size robustness and stability, internal consistency (i.e., split-half reliability), and one-week temporal stability. The psychometric properties of startle potentiation in the NPU task were good but concerns were noted for corrugator potentiation in this task. Some concerns also were noted for the psychometric properties of both startle and corrugator modulation in the Affective Picture Viewing task, in particular for pleasant picture modulation. Psychometric properties of general startle reactivity in the Resting State task were good. Some salient differences in the psychometric properties of the NPU and Affective Picture Viewing tasks were observed within and across quantification methods.

TEMPORAL STABILITY OF ALLOZYME FREQUENCIES IN A NATURAL POPULATION OF DROSOPHILA MELANOGASTER

Genetics ◽  
1981 ◽  
Vol 98 (3) ◽  
pp. 613-623
Author(s):  
Douglas R Cavener ◽  
Michael T Clegg
Keyword(s):  
Drosophila Melanogaster ◽  
Standard Error ◽  
Temporal Stability ◽  
Central Metabolism ◽  
Genetic Condition ◽  
Allelic Variants ◽  
Drosophila Mercatorum ◽  
The Mean ◽  
Parthenogenetic Reproduction ◽  
Frequent Allele

ABSTRACT A Kamuela, Hawaii, population of Drosophila mercatorum was surveyed for enzyme variability. The mean heterozygosity and the proportion of polymorphic loci were estimated as 0.1255 and 0.37, respectively. Neither deviates more than one standard error from their respective means for 43 Drosophila species (Nevo 1978). Heterozygosity was distributed across enzyme categories in much the same manner as observed in other species (Gillespie and Kojima 1968; Johnson 1974), and enzymes associated with glycolysis were about as variable as other enzymes of central metabolism.——The levels of heterozygosity and polymorphism in this population do not seem to have been affected by a low-level capacity for parthenogenesis. The observed parthenogenetic reproduction is not strongly associated with particular allelic variants among viable parthenogenetic adults; however, the capacity to establish a self-sustaining parthenogenetic clone is strongly associated with the phenotype with the most frequent allele at every locus studied. We interpret these results to mean that isozyme variants do not strongly influence viability under total homozygosity (the genetic condition imposed by parthenogenesis), but they do have an impact upon the reproductive biology of parthenogenetic adults.

Sign in / Sign up

Export Citation Format

Share Document