A CHROMOSOMAL ANALYSIS OF X-RAY INDUCED GENETIC VARIANCE OF WING LENGTH IN DROSOPHILA MELANOGASTER

1971 ◽  
Vol 13 (3) ◽  
pp. 600-606
Author(s):  
J. F. Kidwell ◽  
M. L. Tracey ◽  
P. Glaser ◽  
M. M. Kidwell
Keyword(s):  
Sex Differences ◽  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Genetic Variance ◽  
Wing Length ◽  
Chromosomal Analysis ◽  
Isogenic Line ◽  
Additive Variance ◽  
X Ray

A chromosomal analysis of genetic variation in wing length of Drosophila melanogaster was done using an isogenic line and a single derived irradiated line which differed significantly in wing length. Partitioning of the variance indicates no difference between X-ray induced genetic variance and that from other sources. Furthermore, the amount of additive variance is strongly dependent on chromosome frequency, and sex differences are present in all components.

scholarly journals Female Genotypes Affect Sperm Displacement in Drosophila

Genetics ◽  
1998 ◽  
Vol 149 (3) ◽  
pp. 1487-1493 ◽  
Author(s):  
Andrew G Clark ◽  
David J Begun
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Natural Populations ◽  
Isogenic Line ◽  
Female Fitness ◽  
Sperm Displacement ◽  
Extensive Variation ◽  
Polymorphic Genes ◽  
Displacement Parameter ◽  
Competitive Success

Abstract Differential success of sperm is likely to be an important component of fitness. Extensive variation among male genotypes in competitive success of sperm in multiply mated females has been documented for Drosophila melanogaster. However, virtually all previous studies considered the female to be a passive vessel. Nevertheless, under certain conditions female fitness could be determined by her role in mediating use of sperm from multiple males. Here we ask whether females differ among genotypes in their tendency to exhibit last-male precedence. Competition of sperm from two tester male genotypes (bwD and B3-09, a third-chromosome isogenic line from Beltsville, MD) was quantified by doubly mating female lines that had been rendered homozygous for X, second, or third chromosomes isolated from natural populations. The composite sperm displacement parameter, P2′, was highly heterogeneous among lines, whether or not viability effects were compensated, implying the presence of polymorphic genes affecting access of sperm to eggs. Genetic variation of this type is completely neutral in the absence of pleiotropy or interaction between variation in the two sexes.

A NOTE ON KIDWELL'S CHROMOSOMAL ANALYSIS OF EGG PRODUCTION AND CHAETA NUMBER IN DROSOPHILA MELANOGASTER

1970 ◽  
Vol 12 (2) ◽  
pp. 356-358 ◽  
Author(s):  
P. Glaser ◽  
J. F. Kldwell
Keyword(s):  
Drosophila Melanogaster ◽  
Egg Production ◽  
Genetic Variance ◽  
Chromosomal Analysis ◽  
Epistatic Variance

An earlier paper (Kidwell, J.F., 1969, Can. J. Genet. Cytol 11: 547-557) has described partitioning of the genetic variance of egg production and chaeta number in Drosophila melanogaster, assuming equal frequencies of all chromosomes. Kidwell's data were analyzed again, and the new analyses were based on several panmictic populations with varying frequencies for each genotype. The importances of the several portions of the genetic variance were estimated for each population; several cases are presented. In most cases the ranges were substantial, especially those of the dominance and four-factor epistatic variances. The results of the present study generally support Kidwell's previous conclusions and suggest that epistatic variance should not routinely be assumed negligible.

scholarly journals Autosomal and X-Linked Additive Genetic Variation for Lifespan and Aging: Comparisons Within and Between the Sexes in Drosophila melanogaster

2016 ◽  
Vol 6 (12) ◽  
pp. 3903-3911 ◽  
Author(s):  
Robert M Griffin ◽  
Holger Schielzeth ◽  
Urban Friberg
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
X Chromosome ◽  
Dosage Compensation ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Conclusive Evidence ◽  
Substitution Lines ◽  
Chromosome Substitution Lines ◽  
Sexually Antagonistic Selection

Abstract Theory makes several predictions concerning differences in genetic variation between the X chromosome and the autosomes due to male X hemizygosity. The X chromosome should: (i) typically show relatively less standing genetic variation than the autosomes, (ii) exhibit more variation in males compared to females because of dosage compensation, and (iii) potentially be enriched with sex-specific genetic variation. Here, we address each of these predictions for lifespan and aging in Drosophila melanogaster. To achieve unbiased estimates of X and autosomal additive genetic variance, we use 80 chromosome substitution lines; 40 for the X chromosome and 40 combining the two major autosomes, which we assay for sex-specific and cross-sex genetic (co)variation. We find significant X and autosomal additive genetic variance for both traits in both sexes (with reservation for X-linked variation of aging in females), but no conclusive evidence for depletion of X-linked variation (measured through females). Males display more X-linked variation for lifespan than females, but it is unclear if this is due to dosage compensation since also autosomal variation is larger in males. Finally, our results suggest that the X chromosome is enriched for sex-specific genetic variation in lifespan but results were less conclusive for aging overall. Collectively, these results suggest that the X chromosome has reduced capacity to respond to sexually concordant selection on lifespan from standing genetic variation, while its ability to respond to sexually antagonistic selection may be augmented.

Changes in Genetic Variation Induced by Drift

2018 ◽  
Author(s):  
Bruce Walsh ◽  
Michael Lynch
Keyword(s):  
Genetic Variation ◽  
Variance Components ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Additive Variance

In the absence of the input of new variation, drift eventually removes all of the additive-genetic variance in a population. When nonadditive genetic variance is present, some of this variation can be transiently converted into additive variance, resulting in the latter occasionally increasingly (for a time) under inbreeding. This chapter examines the conditions under which such a conversion can occur, which leads to a discussion of the more complex covariances between inbred relatives, requiring the introduction of several new genetic-variance components to be introduced. It also examines the expected equilibrium levels of additive variance under drift-mutation equilibrium.

scholarly journals THE GENETIC VARIANCE FOR VIABILITY AND ITS COMPONENTS IN A LOCAL POPULATION OF DROSOPHILA MELANOGASTER

Genetics ◽  
1974 ◽  
Vol 78 (4) ◽  
pp. 1195-1208
Author(s):  
Terumi Mukai ◽  
Ricardo A Cardellino ◽  
Takao K Watanabe ◽  
James F Crow
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Parameters ◽  
Genetic Variance ◽  
Polymorphic Locus ◽  
Local Population ◽  
Diallel Cross ◽  
Actual Number ◽  
Additive Variance ◽  
Selection For ◽  
Partial Diallel

ABSTRACT Two hundred and ninety second chromosomes extracted from a natural population of Drosophila melanogaster were analyzed to estimate the genetic variance of viability and its components by means of a partial diallel cross (Design II of Comstock and Robinson 1952). The additive and dominance variances are estimated to be 0.009 and 0.0012. Using the dominance variance and the inbreeding depression, the effective number of overdominant loci contributing to the variance in viability is estimated to be very small, a dozen or less. Either the actual number of loci is small, or the distribution of viabilities is strongly skewed with a large majority of very weakly selected loci. The additive variance in viability appears to be too large to be accounted for by recurrent harmful mutants or by overdominant loci at equilibrium with various genetic parameters estimated independently. The excess might be due to frequency-dependent selection, to negative correlations between viability and fertility, or possibly to the presence of a mutator. The selection for viability and fertility, or possibly to the presence of a mutator. The selection for viability at the average polymorphic locus must be very slight, of the order of 10-3 or less.

GENETIC HOMEOSTASIS IN DROSOPHILA MELANOGASTER

1969 ◽  
Vol 11 (2) ◽  
pp. 414-425 ◽  
Author(s):  
P. D. Walton
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Natural Selection ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
The Other ◽  
Diallel Crosses ◽  
Additive Component ◽  
Selection For ◽  
Genetic Homeostasis

The literature provides three explanations of the way in which genetic homeostasis functions. An attempt was made to determine which of these was applicable to the changes which occurred when selection for geotaxis was relaxed in certain strains of Drosophila melonogaster. The strains, for which selection stopped, were divided into two parts and generations were advanced in two environments. One was the same as that in which selection had been made and the other was new. When selection was relaxed strains reverted to a mean geotactic score close to that of the populations from which they had been selected. This change was more rapid in the new environment. A series of diallel crosses compared strains for which selection was continued with those for which it was relaxed. An analysis of the components of genetic variation showed that the principle change that had taken place was in the additive component of genetic variation. It was concluded that genetic homeostasis resulted from the action of natural selection on additive genetic variance, a conclusion which is in agreement with one of the three current hypotheses.

scholarly journals Environmental effects on body size variation in Drosophila melanogaster and its cellular basis

1997 ◽  
Vol 70 (1) ◽  
pp. 35-43 ◽  
Author(s):  
G. H. DE MOED ◽  
G. DE JONG ◽  
W. SCHARLOO
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
Body Size ◽  
Cell Size ◽  
Wing Length ◽  
Size Variation ◽  
Cell Number ◽  
Food Level ◽  
Mean Size ◽  
Food Conditions

Eight isofemale lines of Drosophila melanogaster were raised at four temperatures and at four yeast concentrations in their food. Temperature and food show a significant interaction in determining wing length and thorax length, affecting mean size per line and genetic variation between lines. The combination of low temperature and poor food conditions leads to a sharp increase in the genetic variation over lines of both body size characters. The increase in genetic variation in wing length under less favourable conditions is due to an increase in genetic variation of both cell size and cell number. Changes in wing area in response to both temperature and food level follow a common cell size/cell number trajectory. Changes in wing size are obtained by line-specific changes in the cellular composition of the wing, rather than by changes specific for the environmental factor.

scholarly journals Hidden genetic variance contributes to increase the short-term adaptive potential of selfing populations

2019 ◽  
Author(s):  
Josselin Clo ◽  
Joëlle Ronfort ◽  
Diala Abu Awad
Keyword(s):  
Genetic Variation ◽  
Mutation Rate ◽  
Genetic Variance ◽  
Purifying Selection ◽  
Stabilizing Selection ◽  
Genetic Associations ◽  
Adaptive Potential ◽  
Short Term ◽  
Additive Variance ◽  
Standing Variation

Standing genetic variation is considered a major contributor to the adaptive potential of species. The low heritable genetic variation observed in self-fertilising populations has led to the hypothesis that species with this mating system would be less likely to adapt. However, a non-negligible amount of cryptic genetic variation for polygenic traits, accumulated through negative linkage disequilibrium, could prove to be an important source of standing variation in self-fertilising species. To test this hypothesis we simulated populations under stabilizing selection subjected to an environmental change. We demonstrate that, when the mutation rate is high (but realistic), selfing populations are better able to store genetic variance than outcrossing populations through genetic associations, notably due to the reduced effective recombination rate associated with predominant selfing. Following an environmental shift, this diversity can be partially remobilized, which increases the additive variance and adaptive potential of predominantly (but not completely) selfing populations. In such conditions, despite initially lower observed genetic variance, selfing populations adapt as readily as outcrossing ones within a few generations. For low mutation rates, purifying selection impedes the storage of diversity through genetic associations, in which case, as previously predicted, the lower genetic variance of selfing populations results in lower adaptability compared to their outcrossing counterparts. The population size and the mutation rate are the main parameters to consider, as they are the best predictors of the amount of stored diversity in selfing populations. Our results and their impact on our knowledge of adaptation under high selfing rates are discussed.

scholarly journals Evolutionary genetics of Drosophila melanogaster immunity: role of the X chromosome and sex-specific dominance

2020 ◽  
Author(s):  
Manas Geeta Arun ◽  
Amisha Agarwala ◽  
Jigisha ◽  
Mayank Kashyap ◽  
Saudamini Venkatesan ◽  
...  
Keyword(s):  
Immune Response ◽  
Sex Differences ◽  
Drosophila Melanogaster ◽  
Genetic Variation ◽  
X Chromosome ◽  
Evolutionary Genetics ◽  
Systemic Infection ◽  
Population Level ◽  
Sexual Antagonism

AbstractIntralocus Sexual Conflict (IaSC) ensues when males and females of the same species experience divergent selection on shared traits. A large number of traits have been implicated in IaSC and there is growing evidence for sexual antagonism associated with immunity. X chromosomes are thought to be hotspots of sexually antagonistic genetic variation and have been shown to harbour substantial immunity-related genetic variation.Here, using interpopulation crosses and cytogenetic cloning, we investigated the role of the X chromosome in improved immune response of laboratory populations of the fruit-fly Drosophila melanogaster selected against systemic infection by Pseudomonas entomophila.We could not detect any contribution of the X chromosome in the evolved immune response of our selected populations. However, we found strong evidence of sex-specific dominance related to immunity in our populations. Our results indicate that alleles that confer a superior immune response to the selected populations are, on average, partially dominant in females but partially recessive in males.We argue that sex-specific dominance over immunity evolved as a by-product of sexually antagonistic selection in the wild ancestors of our populations. We also highlight sex-specific dominance as a potential mechanism of sex differences in immunity, with population-level sex differences primarily driven by sex differences in heterozygotes.

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