scholarly journals Polygenic mutation in Drosophila melanogaster: estimates from response to selection of inbred strains.

Genetics ◽  
1994 ◽  
Vol 136 (3) ◽  
pp. 937-951 ◽  
Author(s):  
T F Mackay ◽  
J D Fry ◽  
R F Lyman ◽  
S V Nuzhdin
Keyword(s):  
Drosophila Melanogaster ◽  
Artificial Selection ◽  
Inbred Strains ◽  
Response To Selection ◽  
Environmental Variance ◽  
Rapid Responses ◽  
Bristle Number ◽  
Mutational Variance ◽  
Selection Of ◽  
New Mutations

Abstract Replicated divergent artificial selection for abdominal and sternopleural bristle number from a highly inbred strain of Drosophila melanogaster resulted in an average divergence after 125 generations of selection of 12.0 abdominal and 8.2 sternopleural bristles from the accumulation of new mutations affecting bristle number. Responses to selection were highly asymmetrical, with greater responses for low abdominal and high sternopleural bristle numbers. Estimates of VM, the mutational variance arising per generation, based on the infinitesimal model and averaged over the responses to the first 25 generations of selection, were 4.32 x 10(-3) VE for abdominal bristle number and 3.66 x 10(-3) VE for sternopleural bristle number, where VE is the environmental variance. Based on 10 generations of divergent selection within lines from generation 93, VM for abdominal bristle number was 6.75 x 10(-3) VE and for sternopleural bristle number was 5.31 x 10(-3) VE. However, estimates of VM using the entire 125 generations of response to selection were lower and generally did not fit the infinitesimal model largely because the observed decelerating responses were not compatible with the predicted increasing genetic variance over time. These decelerating responses, periods of response in the opposite direction to artificial selection, and rapid responses to reverse selection all suggest new mutations affecting bristle number on average have deleterious effects on fitness. Commonly observed periods of accelerated responses followed by long periods of stasis suggest a leptokurtic distribution of mutational effects for bristles.

scholarly journals The response to artificial selection from new mutations in Drosophila melanogaster.

Genetics ◽  
1991 ◽  
Vol 128 (1) ◽  
pp. 89-102 ◽  
Author(s):  
A Caballero ◽  
M A Toro ◽  
C López-Fanjul
Keyword(s):  
Drosophila Melanogaster ◽  
Single Mutation ◽  
Effective Population ◽  
Environmental Variance ◽  
Epistatic Interactions ◽  
Bristle Number ◽  
Population Sizes ◽  
Selection For ◽  
Mutational Variance ◽  
New Mutations

Abstract Twenty generations of divergent selection for abdominal bristle number were carried out starting from a completely homozygous population of Drosophila melanogaster. All lines were selected with the same proportion (20%) but at two different numbers of selected parents of each sex (5 or 25). A significant response to selection was detected in eight lines (out of 40) and, in most cases, it could be wholly attributed to a single mutation of relatively large effect (0.5-2 phenotypic standard deviations). The ratio of new mutational variance to environmental variance was estimated to be (0.33 +/- 0.11) X 10(-3). The distribution of mutant effects was asymmetrical, both with respect to bristle number (85% of it was negative) and to fitness (most detected bristle mutations were lethal or semilethal). Moreover, this distribution was leptokurtic, due to the presence of major genes. Gene action on bristles ranged from additive to completely recessive, no epistatic interactions being found. In agreement with theory, larger responses in each direction were achieved by those lines selected at greater effective population sizes. Furthermore, the observed divergence between lines selected in opposite directions was proportional to their effective size, as predicted for mutations of large effect.

scholarly journals The distribution of spontaneous mutations on quantitative traits and fitness in Drosophila melanogaster.

Genetics ◽  
1992 ◽  
Vol 132 (3) ◽  
pp. 771-781 ◽  
Author(s):  
E Santiago ◽  
J Albornoz ◽  
A Domínguez ◽  
M A Toro ◽  
C López-Fanjul
Keyword(s):  
Drosophila Melanogaster ◽  
Single Mutation ◽  
Environmental Variance ◽  
Recessive Mutations ◽  
Bristle Number ◽  
Additive Action ◽  
Wing Width ◽  
Mutational Variance ◽  
Similar Gene ◽  
Apparent Association

Abstract Starting from a completely homozygous population of Drosophila melanogaster, two groups of 100 inbred lines each were established and maintained for 46 generations, by a single brother-sister mating and two double first cousin matings, respectively. Sternopleural bristle number, wing length and wing width were simultaneously scored in all lines every 4-5 generations. The means of four lines in each group departed significantly from the overall mean and, in each case, this was attributed to a single mutation of relatively large effect on at least one trait (0.3-1.4 environmental standard deviations in absolute value). Further analyses revealed widespread pleiotropy, similar gene action of a given mutation for all traits affected, and predominant additive action. No apparent association was found between the magnitudes of mutational effects on the traits and fitness. However, all recessive mutations were deleterious. The distribution of mutant effects was asymmetrical (positive for bristles and negative for wing measurements). Moreover, these distributions had a high variance and may be leptokurtic, due to the presence of major genes. Estimates of the ratio of new mutational variance to environmental variance ranged within (0.7-3.4) x 10(-3), those for wing measurements being generally larger. In agreement with theory, the rate of between-line differentiation was independent of population size.

scholarly journals Spontaneous mutation for a quantitative trait in Drosophila melanogaster. I. Response to artificial selection

1993 ◽  
Vol 61 (2) ◽  
pp. 107-116 ◽  
Author(s):  
María A. López ◽  
Carlos López-Fanjul
Keyword(s):  
Drosophila Melanogaster ◽  
Large Fraction ◽  
Spontaneous Mutation ◽  
Single Mutation ◽  
Effective Population ◽  
Environmental Variance ◽  
Bristle Number ◽  
Population Sizes ◽  
Selection For ◽  
Mutational Variance

SummaryDivergent selection for abdominal bristle number was carried out for 47 generations, starting from a completely homozygous population of Drosophila melanogaster. All lines were selected with the same proportion (20%) but at two different numbers of selected parents of each sex (5 or 25). A significant response to selection was obtained in 25 lines (out of 40). In most cases, it could be wholly attributed to a single mutation of relatively large effect (> 0·3 phenotypic standard deviations). A total number of 30 mutations were detected. In agreement with theory, larger responses in each direction were achieved by those lines selected at greater effective population sizes. A large fraction of mutations were lethals (10/30). Thus, the observed divergence between lines of the same effective size selected in opposite directions was smaller than expected under neutrality. The ratio of new mutational variance to environmental variance was estimated to be(0·52±0·09)×10−3.

scholarly journals Temporal uniformity of the spontaneous mutational variance of quantitative traits in Drosophila melanogaster

2000 ◽  
Vol 75 (1) ◽  
pp. 47-51 ◽  
Author(s):  
AURORA GARCÍA-DORADO ◽  
JESUS FERNÁNDEZ ◽  
CARLOS LÓPEZ-FANJUL
Keyword(s):  
Drosophila Melanogaster ◽  
Morphological Traits ◽  
Quantitative Traits ◽  
Wing Length ◽  
Environment Interaction ◽  
Genotype Environment Interaction ◽  
Bristle Number ◽  
Sib Mating ◽  
Mutational Variance ◽  
Interaction Variance

Spontaneous mutations were allowed to accumulate over 209 generations in more than 100 lines, all of them independently derived from a completely homozygous population of Drosophila melanogaster and subsequently maintained under strong inbreeding (equivalent to full-sib mating). Traits scored were: abdominal (AB) and sternopleural (ST) bristle number, wing length (WL) and egg-to-adult viability (V). On two occasions – early (generations 93–122) and late (generations 169–209) – ANOVA estimates of the mutational variance and the mutational line × generation interaction variance were obtained. Mutational heritabilities of morphological traits ranged from 2 × 10−4 to 2 × 10−3 and the mutational coefficient of variation of viability was 0·01. For AB, WL and V, temporal uniformity of the mutational variance was observed. However, a fluctuation of the mutational heritability of ST was detected and could be ascribed to random genotype × environment interaction.

scholarly journals Effects of Artificial Selection on Rates of Inbreeding in Populations of Drosophila Melanogaster

1969 ◽  
Vol 22 (1) ◽  
pp. 143 ◽  
Author(s):  
LP Jones
Keyword(s):  
Drosophila Melanogaster ◽  
Artificial Selection ◽  
Bristle Number ◽  
Seven Generations

The rate of inbreeding was studied using the conventional F value, as well as the "percentage of genes" technique of James and McBride (1958), in lines of D. melanogaster selected for increased abdominal bristle number for seven generations at intensities of 10, 20, and 50% with 10 pairs of parents.

scholarly journals Response to Selection in Synthetic Lines of Drosophila Melanogaster

1973 ◽  
Vol 26 (3) ◽  
pp. 613 ◽  
Author(s):  
RR Howe ◽  
JW James
Keyword(s):  
Drosophila Melanogaster ◽  
Base Population ◽  
Response To Selection ◽  
Bristle Number ◽  
Experimental Analyses

Response to selection in synthetic lines has been examined by both theoretical and experimental analyses. Synthetic lines were founded from 20 base lines of D. melanogaster all derived from the same base population and which had been selected for high sternopleural bristle number.

THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. XV. NATURE OF DEVELOPMENTAL HOMEOSTASIS FOR VIABILITY

Genetics ◽  
1982 ◽  
Vol 101 (2) ◽  
pp. 279-300
Author(s):  
Terumi Mukai ◽  
Sadao I Chigusa ◽  
Shin-Ichi Kusakabe
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Populations ◽  
Error Variance ◽  
Sampling Variance ◽  
Environmental Variance ◽  
Developmental Homeostasis ◽  
Relative Viability ◽  
The Difference ◽  
Two Populations ◽  
New Mutations

ABSTRACT Developmental homeostasis of relative viability was examined for homozygotes and heterozygotes using second chromosomes from two populations of Drosophila melanogaster. One was a chromosome population in which spontaneous mutations were allowed to accumulate since it was begun with a single near-normal second chromosome. The second was a natural population approximately at equilibrium. For the estimation of relative viability, the Cy method was employed (Wallace 1956), and environmental variance between simultaneously replicated cultures was used as the index of developmental homeostasis. A new method was used in the estimation of sampling variance for relative viability that was employed for the calculation of environmental variance (error variance between simultaneously replicated cultures — sampling variance). The following findings were obtained.: (1) The difference in environmental variance between homozygotes and heterozygotes could not be seen when a chromosome population with variation due to new mutations was tested. (2) When a chromosome group isolated from an approximate equilibrium population was examined, heterozygotes manifested a smaller environmental variance than the homozygotes if their relative viabilities were approximately the same. (3) There was a slight negative correlation between viability and environmental variance, although opposite results were found when the viabilities of individuals were high, especially when overdominance (coupling overdominance, Mukai 1969 a, b) was manifest. On the basis of these findings, it was concluded that developmental homeostasis was a product of natural selection, and its mechanism was discussed.

scholarly journals The genetic analysis of the direct and correlated response to selection for chaetae in Drosophila melanogaster

1973 ◽  
Vol 22 (1) ◽  
pp. 1-7
Author(s):  
W. R. Scowcroft
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Analysis ◽  
Genetic Correlation ◽  
Statistical Approach ◽  
Correlated Response ◽  
Minor Importance ◽  
Response To Selection ◽  
Genetic Changes ◽  
Selection For ◽  
Selection Of

SUMMARYThe direct and correlated response to selection of scutellar microchaetae and scutellar bristles has been analysed by determining the contribution of the three major chromosomes, alone and in combination with each other, to the overall response. The results of the analysis confirm a previous finding, based on a formal statistical approach, that response to selection for microchaetae had highly pleiotropic effects on scutellar bristles. In lines selected, each for high and low microchaetae, genetic changes in the 2nd and 3rd chromosomes are pre-eminent and essentially equal. Inter-chromosomal interactions are of relatively minor importance in interpreting the response to selection for microchaetae but assume greater importance with respect to the correlated character. The results are discussed in terms of the genetic correlation between fitness and the character measured.

scholarly journals Effects of linkage on response to directional selection from new mutations

1983 ◽  
Vol 42 (2) ◽  
pp. 193-206 ◽  
Author(s):  
P. D. Keightley ◽  
W. G. Hill
Keyword(s):  
Quantitative Traits ◽  
Directional Selection ◽  
Small Populations ◽  
Additive Effects ◽  
Steady Rate ◽  
Mutant Genes ◽  
Mutational Variance ◽  
Rate Of Response ◽  
Selection Of ◽  
New Mutations

SUMMARYThe influence of linkage on the rates of response to continued directional selection of quantitative traits deriving from variation contributed by new mutations in finite populations is investigated. Mutant genes are assumed to have additive effects which are randomly sampled from a symmetric distribution, and to be randomly located on the chromosome. Results were obtained by Monte Carlo simulation.The expected steady rate of response, when variability from new mutations is balanced by that lost by drift and selection, is reduced the tighter the linkage, but the reduction is small unless there are few, short chromosomes. For a given rate of new mutational variance per haploid chromosome set per generation, greater effects of linkage are obtained in large than in small populations, because more mutants segregate. The response and influence of linkage are essentially the same whether the new variance is due to many genes of small effect or few of large effect.The variability of response between replicates and generations was investigated, and the contribution to this of new mutants or recombination of existing mutants compared. Usually most genetic variability was due to the occurrence of a new favourable mutant of large effect.

scholarly journals Heritability of Directional Asymmetry in Drosophila melanogaster

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Ashley J. R. Carter ◽  
Elizabeth Osborne ◽  
David Houle
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Artificial Selection ◽  
Natural Variation ◽  
The Other ◽  
Directional Asymmetry ◽  
Consistent Difference ◽  
Selection Experiment ◽  
Response To Selection ◽  
Powerful Technique

Directional asymmetry (DA), the consistent difference between a pair of morphological structures in which the same side is always larger than the other, presents an evolutionary mystery. Although many paired traits show DA, genetic variation for DA has not been unambiguously demonstrated. Artificial selection is a powerful technique for uncovering selectable genetic variation; we review and critique the limited number of previous studies that have been performed to select on DA and present the results of a novel artificial selection experiment on the DA of posterior crossvein location in Drosophila wings. Fifteen generations of selection in two genetically distinct lines were performed and none of the lines showed a significant response to selection. Our results therefore support and reconfirm previous findings; despite apparent natural variation and evolution of DA in nature, DA remains a paradoxical trait that does not respond to artificial selection.

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