scholarly journals TESTING FOR SELECTIVE NEUTRALITY OF ELECTROPHORETICALLY DETECTABLE PROTEIN POLYMORPHISMS

Genetics ◽  
1976 ◽  
Vol 84 (3) ◽  
pp. 639-659
Author(s):  
B S Weir ◽  
A H D Brown ◽  
D R Marshall
Keyword(s):  
Charge State ◽  
Neutral Theory ◽  
Natural Populations ◽  
State Model ◽  
Model Parameters ◽  
Simulation Data ◽  
Chi Square ◽  
Electrophoretic Mobilities ◽  
Selective Neutrality ◽  
Protein Polymorphisms

ABSTRACT The statistical assessment of gene-frequency data on protein polymorphisms in natural populations remains a contentious issue. Here we formulate a test of whether polymorphisms detected by electrophoresis are in accordance with the stepwise, or charge-state, model of mutation in finite populations in the absence of selection. First, estimates of the model parameters are derived by minimizing chi-square deviations of the observed frequencies of genotypes with alleles (0,1,2…) units apart from their theoretical expected values. Then the remaining deviation is tested under the null hypothesis of neutrality. The procedure was found to be conservative for false rejections in simulation data. We applied the test to Ayala and Tracey 's data on 27 allozymic loci in six populations of Drosophila willistoni. About one-quarter of polymorphic loci showed significant departure from the neutral theory predictions in virtually all populations. A further quarter showed significant departure in some populations. The remaining data showed an acceptable fit to the charge state model. A predominating mode of selection was selection against alleles associated with extreme electrophoretic mobilities. The advantageous properties and the difficulties of the procedure are discussed.

scholarly journals Profiles of electrophoretic alleles in natural populations

1975 ◽  
Vol 25 (2) ◽  
pp. 137-143 ◽  
Author(s):  
A. H. D. Brown ◽  
D. R. Marshall ◽  
L. Albrecht
Keyword(s):  
Charge State ◽  
Frequency Distribution ◽  
Finite Population ◽  
Natural Populations ◽  
State Model ◽  
Geometric Series ◽  
Effective Number ◽  
Expected Frequency ◽  
Central Moments

SUMMARYThe charge state model of Ohta & Kimura (1973) for the number of electrophoretically detectable alleles in a finite population, is extended to include mutations of both one and two charge changes. The effective number of alleles (ne) is increased only slightly by this extension. Electrophoretic profiles of neutral variants are shown on average to be leptokurtic and have their odd central moments equal to zero. The expected frequency distribution of pairs of gametes which differ by 1,2,3,… charge units can be obtained as the sum of the appropriate terms from two geometric series.

scholarly journals GENETIC VARIATION IN NATURAL POPULATIONS OF FIVE DROSOPHILA SPECIES AND THE HYPOTHESIS OF THE SELECTIVE NEUTRALITY OF PROTEIN POLYMORPHISMS

Genetics ◽  
1974 ◽  
Vol 77 (2) ◽  
pp. 343-384
Author(s):  
Francisco J Ayala ◽  
Martin L Tracey ◽  
Lorraine G Barr ◽  
John F McDonald ◽  
Santiago Pérez-Salas
Keyword(s):  
Genetic Variation ◽  
Genetic Differentiation ◽  
Natural Populations ◽  
Evolutionary Divergence ◽  
Average Value ◽  
Local Populations ◽  
Selective Neutrality ◽  
Average Proportion ◽  
Substantial Degree ◽  
Protein Polymorphisms

ABSTRACT We have studied genetic variation at 30-32 loci coding for enzymes in natural populations of five species of Drosophila. The average proportion of heterozygous loci per individual is 17.7 ± 0.4%. The average proportion of polymorphic loci per population is 69.2 ± 2.6% or 49.8 ± 2.2%, depending on what criterion of polymorphism is used. The following generalizations are advanced: (1) The amount of genetic polymorphism varies considerably from locus to locus. (2) At a given locus, populations of the same species are very similar in the amount and pattern of genetic variation. (3) However, at some loci large differences sometimes occur between local populations of the same species. (4) The amount of variation at a given locus is approximately the same in all five species. (5) When different species are compared, the pattern of the variation is either essentially identical or totally different at a majority of loci. We have tested the hypothesis that protein polymorphisms are selectively neutral by examining four predictions derived from the hypothesis. Our results are at variance with every one of the predictions. We have measured the amount of genetic differentiation, D, between taxa of various degrees of evolutionary divergence. The average value of D is 0.033 for local populations, 0.228 for subspecies, 0.226 for semispecies, 0.538 for sibling species, and 1.214 for morphologically distinguishable species. Our results indicate that a substantial degree of genetic differentiation (22.8 allelic substitutions for every 100 loci) occurs between allopatric populations that have diverged to the point where they might become different species if they were to become sympatric. However, very little additional genetic change is required for the development of complete reproductive isolation. After the speciation process is completed, species continue to diverge genetically from each other.

scholarly journals Inferring Linkage Disequilibrium Between a Polymorphic Marker Locus and a Trait Locus in Natural Populations

Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 457-467 ◽  
Author(s):  
Z W Luo ◽  
S H Tao ◽  
Z-B Zeng
Keyword(s):  
Linkage Disequilibrium ◽  
Allele Frequency ◽  
Random Mating ◽  
Natural Populations ◽  
Polymorphic Marker ◽  
Marker Locus ◽  
Model Parameters ◽  
Phenotypic Variance ◽  
Wide Range ◽  
Trait Locus

Abstract Three approaches are proposed in this study for detecting or estimating linkage disequilibrium between a polymorphic marker locus and a locus affecting quantitative genetic variation using the sample from random mating populations. It is shown that the disequilibrium over a wide range of circumstances may be detected with a power of 80% by using phenotypic records and marker genotypes of a few hundred individuals. Comparison of ANOVA and regression methods in this article to the transmission disequilibrium test (TDT) shows that, given the genetic variance explained by the trait locus, the power of TDT depends on the trait allele frequency, whereas the power of ANOVA and regression analyses is relatively independent from the allelic frequency. The TDT method is more powerful when the trait allele frequency is low, but much less powerful when it is high. The likelihood analysis provides reliable estimation of the model parameters when the QTL variance is at least 10% of the phenotypic variance and the sample size of a few hundred is used. Potential use of these estimates in mapping the trait locus is also discussed.

Evidence against the negative-charge-state model for theDXcenter inn-type GaAs

1989 ◽  
Vol 62 (16) ◽  
pp. 1922-1922 ◽  
Author(s):  
D. K. Maude ◽  
L. Eaves ◽  
T. J. Foster ◽  
J. C. Portal
Keyword(s):  
Charge State ◽  
Negative Charge ◽  
State Model

scholarly journals Nucleotide sequences of highly repeated DNAs; compilation and comments

1982 ◽  
Vol 39 (1) ◽  
pp. 1-30 ◽  
Author(s):  
George L. Gabor Miklos ◽  
Amanda Clare Gill
Keyword(s):  
Satellite Dna ◽  
Germ Line ◽  
Sequence Data ◽  
Allelic Variation ◽  
Neutral Theory ◽  
Natural Populations ◽  
Evolutionary Significance ◽  
Nucleotide Sequence Data ◽  
A Genome ◽  
Repeated Dnas

SummaryThe nucleotide sequence data from highly repeated DNAs of inverte-brates and mammals are summarized and briefly discussed. Very similar conclusions can be drawn from the two data bases. Sequence complexities can vary from 2 bp to at least 359 bp in invertebrates and from 3 bp to at least 2350 bp in mammals. The larger sequences may or may not exhibit a substructure. Significant sequence variation occurs for any given repeated array within a species, but the sources of this heterogeneity have not been systematically partitioned. The types of alterations in a basic repeating unit can involve base changes as well as deletions or additions which can vary from 1 bp to at least 98 bp in length. These changes indicate that sequence per se is unlikely to be under significant biological constraints and may sensibly be examined by analogy to Kimura's neutral theory for allelic variation. It is not possible with the present evidence to discriminate between the roles of neutral and selective mechanisms in the evolution of highly repeated DNA.Tandemly repeated arrays are constantly subjected to cycles of amplification and deletion by mechanisms for which the available data stem largely from ribosomal genes. It is a matter of conjecture whether the solutions to the mechanistic puzzles involved in amplification or rapid redeployment of satellite sequences throughout a genome will necessarily give any insight into biological functions.The lack of significant somatic effects when the satellite DNA content of a genome is significantly perturbed indicates that the hunt for specific functions at the cellular level is unlikely to prove profitable.The presence or in some cases the amount of satellite DNA on a chromosome, however, can have significant effects in the germ line. There the data show that localized condensed chromatin, rich in satellite DNA, can have the effect of rendering adjacent euchromatic regions rec−, or of altering levels of recombination on different chromosomes. No data stemming from natural populations however are yet available to tell us if these effects are of adaptive or evolutionary significance.

scholarly journals Determination of GTN Model Parameters Based on Artificial Neutral Network for a Ductile Failure

2021 ◽  
Vol 2 (1) ◽  
pp. 01-05
Author(s):  
YASSINE CHAHBOUB ◽  
SZAVAI Szabolcs
Keyword(s):  
Ductile Failure ◽  
Compact Tension ◽  
Model Parameters ◽  
Single Edge ◽  
Direct Identification ◽  
Simulation Data ◽  
Short Period ◽  
Artificial Neural Network Ann ◽  
Excellent Tool

The Gurson – Tvergaard – Needleman (GTN) mechanical model is widely used to predict the failure of materials based on laboratory specimens, direct identification of Gurson – Tvergaard – Needleman parameters is not easy and time-consuming, and the most used method to determine them is the combination between the experimental results and those of the finite elements, the process consists of repeating the simulations several times until the simulation data matches the experimental data obtained at the specimen level.This article aims to find GTN parameters for the Compact Tension (CT) and Single Edge Tensile Test (SENT) specimen based on the Notch Specimen (NT) using the Artificial Neural Network (ANN) approach. . This work presents how the ANN could help us determine the parameters of GTN in a very short period of time. The results obtained show that ANN is an excellent tool for determining GTN parameters.

scholarly journals Ploidy frequencies in plants with ploidy heterogeneity: fitting a general gametic model to empirical population data

2013 ◽  
Vol 280 (1751) ◽  
pp. 20122387 ◽  
Author(s):  
Jan Suda ◽  
Tomáš Herben
Keyword(s):  
Natural Populations ◽  
Evolutionary Process ◽  
Optimization Procedure ◽  
Population Data ◽  
Unreduced Gametes ◽  
Unreduced Gamete ◽  
Model Parameters ◽  
Main Mode ◽  
Ploidy Levels ◽  
Polyploid Formation

Genome duplication (polyploidy) is a recurrent evolutionary process in plants, often conferring instant reproductive isolation and thus potentially leading to speciation. Outcome of the process is often seen in the field as different cytotypes co-occur in many plant populations. Failure of meiotic reduction during gametogenesis is widely acknowledged to be the main mode of polyploid formation. To get insight into its role in the dynamics of polyploidy generation under natural conditions, and coexistence of several ploidy levels, we developed a general gametic model for diploid–polyploid systems. This model predicts equilibrium ploidy frequencies as functions of several parameters, namely the unreduced gamete proportions and fertilities of higher ploidy plants. We used data on field ploidy frequencies for 39 presumably autopolyploid plant species/populations to infer numerical values of the model parameters (either analytically or using an optimization procedure). With the exception of a few species, the model fit was very high. The estimated proportions of unreduced gametes (median of 0.0089) matched published estimates well. Our results imply that conditions for cytotype coexistence in natural populations are likely to be less restrictive than previously assumed. In addition, rather simple models show sufficiently rich behaviour to explain the prevalence of polyploids among flowering plants.

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