scholarly journals Langzeitselektion bei asymmetrischer Merkmalsverteilung

2000 ◽  
Vol 43 (5) ◽  
pp. 421-430
Author(s):  
N. Mielenz ◽  
L. Schüler
Keyword(s):  
Quantitative Trait ◽  
Mixed Model ◽  
Major Effect ◽  
Polygenic Effect ◽  
Phenotypic Variance ◽  
Environment Interaction ◽  
Term Selection ◽  
Wide Range ◽  
Skewness And Kurtosis

Abstract. Title of the paper: Long-term selection by asymmetric trait distribution A quantitative trait is assumed to be genetically affected by a polygenic effect and a major effect of a Single dialellic locus. Such a model is called mixed model of inheritance and the identified gene is denoted as quantitative trait locus (QTL). By choosing the part of the QTL-variance, the degree of dominance and the frequency of the favourable allele it is possible to generate distributions with given level of asymmetry characterised by skewness and kurtosis. If the ratio of QTL- and phenotypic variance is small (less than 8%), then genotype-environment interaction can be used in the mixed inheritance model to explain values of skewness and kurtosis estimated with poultry data. The Situation is considered where the environmental variances given for the three QTL-genotypes show a wide ränge. In most of these cases the short- and long-term selection does not effects the high values for skewness and kurtosis over multiple generations. Further the ratio of response to selection and the difference of selection depends on the selection intensity.

scholarly journals Nutzung von QTL-Information bei der Langzeitselektion

2002 ◽  
Vol 45 (1) ◽  
pp. 87-97
Author(s):  
N. Mielenz ◽  
L. Schüler
Keyword(s):  
Quantitative Trait ◽  
Optimal Strategies ◽  
Phenotypic Selection ◽  
Major Effect ◽  
Breeding Value ◽  
Polygenic Effect ◽  
Genetic Changes ◽  
Infinite Population ◽  
Trait Locus

Abstract. Title of the paper: Long-term selection by using QTL-information A quantitative trait is assumed to be genetically affected by a polygenic effect and a major effect of a single dialellic locus. Such an identified gene is denoted as quantitative trait locus (QTL). A population characterized by infinite population size, heritability equal to 0.4, ratio of QTL-variance and total genetic variance equal to 20 % and complete dominance at the QTL was considered. The objective of the study was to investigate the genetic changes in the population over 20 generations of selection in five different environmental situations. The scenarios differed in the environmental variation of the three QTL-genotypes and also in heritability level after the favourable allel being fixed. To selection over generations indexes were constructed including the breeding value for the known QTL, the genotypic value of the QTL and the estimated polygenic breeding value. Beside of selection on phenotype and standard-indexes a sub-optimal index contracted the environmental variances at the QTL was considered in the model. If the favourable QTL-genotype is highly affected by the environment than it can be of advantage to select against the favourable allel. Deterministic calculations confirmed greater long-term response for sub-optimal strategies over standard indexes and phenotypic selection, not only for the up-selection but for the down-selection as well. The results from the deterministic approach showed good agreements with the results obtained by stochastic simulation.

scholarly journals Effects of leptin administration on long-term selected fat mice

1997 ◽  
Vol 69 (3) ◽  
pp. 215-225 ◽  
Author(s):  
LUTZ BÜNGER ◽  
WILLIAM G. HILL
Keyword(s):  
Matter Content ◽  
Control Line ◽  
Dry Matter Content ◽  
Genetic Changes ◽  
Term Selection ◽  
Wide Range ◽  
Selection For ◽  
Phosphate Buffered Saline

To assess the role of genetic changes in sensitivity to leptin hormone in contributing to responses to long-term selection for fatness, leptin was administered to a long-term fat selected (F) and a control line (C) of mice. These lines differ almost three fold in their percentage of fat (fat%) at about 15 weeks of age. Treated (T) animals received twice-daily intraperitoneal injections of 5 mg/kg leptin from 91 to 105 days of age; untreated (U) animals received equivolume injections of phosphate-buffered saline. Treated compared with untreated animals in both lines had significantly (P<0·05) lower mean body weight, food intake and fatness at the end of test (fat%: CT 3%, CU 7·4%, FT 14·9%, FU21·1%). The differences in response between the lines [(CT−CU)−(FT−FU)] were all non-significant (P>0·05), however. There was a very wide range of fatness (estimated from dry matter content) among FT animals (3–29%), much higher than in FU (15–31%), CT (0·7–6·4%) and CU (2–15%) animals. While sensitivity to leptin remains in the fat line, response appears to vary among animals at the dose level used.

scholarly journals Impacto da Aplicação em Ativos Internacionais no Desempenho dos Fundos de Pensão no Brasil

2009 ◽  
Vol 7 (2) ◽  
pp. 237
Author(s):  
Raphael Braga Silva ◽  
Roberto Moreno Moreira ◽  
Luiz Felipe Jacques Motta
Keyword(s):  
Hedge Funds ◽  
Efficient Frontier ◽  
Pension Funds ◽  
Major Effect ◽  
Economic Environment ◽  
Financial Health ◽  
Wide Range ◽  
Asset Classes ◽  
International Assets

The present study has performed an analysis of the effects caused in the performance of Brazilian pension funds by the inclusion of international assets in their portfolios. The Resolution CMN 3456 of June 1, 2007 allowed pension funds in Brazil to allocate up to 3% of their investments in international hedge funds. Given the wide range of assets classes available in this category of hedge funds, this study has focused on international assets. The investments in such asset classes do not generate a major effect on the efficient frontier of the pension funds’ investments. The results do not change much even if we increase the constraint from 3% to 20%. However, changes in the current economic environment indicate that finding alternative investments that can enhance the asset performance on a long term view will be a crucial factor to maintain the financial health of pension funds.

scholarly journals Permutation Testing in the Presence of Polygenic Variation

2015 ◽  
Author(s):  
Mark Abney
Keyword(s):  
Quantitative Trait ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Permutation Test ◽  
Statistical Significance ◽  
Null Distribution ◽  
Polygenic Effect ◽  
Permutation Testing ◽  
Test Statistic ◽  
Omnibus Test

This article discusses problems with and solutions to performing valid permutation tests for quantitative trait loci in the presence of polygenic effects. Although permutation testing is a popular approach for determining statistical significance of a test statistic with an unknown distribution--for instance, the maximum of multiple correlated statistics or some omnibus test statistic for a gene, gene-set or pathway--naive application of permutations may result in an invalid test. The risk of performing an invalid permutation test is particularly acute in complex trait mapping where polygenicity may combine with a structured population resulting from the presence of families, cryptic relatedness, admixture or population stratification. I give both analytical derivations and a conceptual understanding of why typical permutation procedures fail and suggest an alternative permutation based algorithm, MVNpermute, that succeeds. In particular, I examine the case where a linear mixed model is used to analyze a quantitative trait and show that both phenotype and genotype permutations may result in an invalid permutation test. I provide a formula that predicts the amount of inflation of the type 1 error rate depending on the degree of misspecification of the covariance structure of the polygenic effect and the heritability of the trait. I validate this formula by doing simulations, showing that the permutation distribution matches the theoretical expectation, and that my suggested permutation based test obtains the correct null distribution. Finally, I discuss situations where naive permutations of the phenotype or genotype are valid and the applicability of the results to other test statistics.

scholarly journals Using the mixed model for interval mapping of quantitative trait loci in outbred line crosses

2001 ◽  
Vol 77 (2) ◽  
pp. 199-207 ◽  
Author(s):  
Y. NAGAMINE ◽  
C. S. HALEY
Keyword(s):  
Animal Model ◽  
Quantitative Trait Loci ◽  
Qtl Analysis ◽  
Quantitative Trait ◽  
Fixed Effects ◽  
Mixed Model ◽  
Interval Mapping ◽  
Estimation Methods ◽  
Polygenic Effect ◽  
Trait Loci

Interval mapping by simple regression is a powerful method for the detection of quantitative trait loci (QTLs) in line crosses such as F2 populations. Due to the ease of computation of the regression approach, relatively complex models with multiple fixed effects, interactions between QTLs or between QTLs and fixed effects can easily be accommodated. However, polygenic effects, which are not targeted in QTL analysis, cannot be treated as random effects in a least squares analysis. In a cross between true inbred lines this is of no consequence, as the polygenic effect contributes just to the residual variance. In a cross between outbred lines, however, if a trait has high polygenic heritability, the additive polygenic effect has a large influence on variation in the population. Here we extend the fixed model for the regression interval mapping method to a mixed model using an animal model. This makes it possible to use not only the observations from progeny (e.g. F2), but also those from the parents (F1) to evaluate QTLs and polygenic effects. We show how the animal model using parental observations can be applied to an outbred cross and so increase the power and accuracy of QTL analysis. Three estimation methods, i.e. regression and an animal model either with or without parental observations, are applied to simulated data. The animal model using parental observations is shown to have advantages in estimating QTL position and additive genotypic value, especially when the polygenic heritability is large and the number of progeny per parent is small.

scholarly journals Long-term selection for protein amount over 70 generations in mice

1998 ◽  
Vol 72 (2) ◽  
pp. 93-109 ◽  
Author(s):  
LUTZ BÜNGER ◽  
ULLA RENNE ◽  
GERHARD DIETL ◽  
SIEGFRIED KUHLA
Keyword(s):  
Body Weight ◽  
Selection Response ◽  
Direct Selection ◽  
Control Line ◽  
Phenotypic Variance ◽  
Effective Population ◽  
Term Selection ◽  
General Importance ◽  
Selection For

Based on the outbred mouse strain Fzt: Du, which has been obtained by systematic crossing of four inbred and four outbred lines, a long-term selection experiment was carried out for total protein amount (PA) in the carcass, starting in 1975. An unselected control line (CO) was kept under the same management but without continuous protein analysis. The protein amount of male carcasses at 42 days of age (P42) increased from 2·9 g in generation 0 to 5·2 g at generation 70, representing 97% of a theoretical selection limit. The total selection response amounts to 2·3 g, which is about 80% above the initial value and corresponds to 9σp or 12σA . The estimated realized heritability of protein amount decreased from 0·56 to 0·03 at generation 70, which was due to an increase in phenotypic variance from 0·065 to 0·24 g2 and a reduction in genetic variance from 0·04 to 0·01 g2. Half the selection response was obtained after about 18 to 23 generations, a half-life of 0·25 to 0·3 Ne. The maximum selection response was 0·094 g/generation and the response was 0·01 g/generation at generation 70. The measurements of body weights at 0, 10, 21, 42 and 63 days throughout the experiment showed a strong correlated effect for all weights. The PA mice are one of the heaviest lines of mice ever reported, and do not differ significantly in their body composition from control mice at 42 days. The direct selection response was due primarily to increased general growth. Body weight and protein amount are phenotypically and genetically highly correlated (rp=0·82, rA≈1); however, selection for body weight led to fatter animals, whereas selection for protein opposed increased fatness (at least until selection age). This may be of general importance in animal breeding. The comparatively high selection response in this experiment seems due to the heterogeneity of the base population, the relatively high effective population size, and the duration of the experiment.

The analysis of quantitative trait loci in multi-environment trials using a multiplicative mixed model

2003 ◽  
Vol 54 (12) ◽  
pp. 1395 ◽  
Author(s):  
A. P. Verbyla ◽  
P. J. Eckermann ◽  
R. Thompson ◽  
B. R. Cullis
Keyword(s):  
Program Analysis ◽  
Quantitative Trait ◽  
Mixed Model ◽  
Genetic Model ◽  
Random Effect ◽  
Doubled Haploid Population ◽  
Environment Interaction ◽  
Factor Analytic Model ◽  
Factor Analytic ◽  
Trait Locus

A new approach for multi-environment quantitative trait locus (QTL) analysis based on an appropriate genetic model is presented. To accommodate a multi-environment analysis, the size of a QTL effect is assumed to be a random effect. The approach results in a multiplicative mixed model for QTL × environment interaction of the factor analytic type. The full genetic model may also include a factor analytic model for the residual genotype × environment interaction, whereas the environmental model for the non-genetic variation involves local, global, and extraneous variation. The approach is used to determine QTLs for yield in the Arapiles × Franklin doubled haploid population of the National Barley Molecular Marker Program. Analysis leads to the determination of 8 QTLs. Many of these QTLs are associated with other traits.

scholarly journals Estimation of Additive and Non-Additive Genetic Variances of Body Weight, Egg Weight and Egg Production for Quails (Coturnix coturnix japonica) with an Animal Model Analysis

2006 ◽  
Vol 49 (3) ◽  
pp. 300-307 ◽  
Author(s):  
N. Mielenz ◽  
R. R. Noor ◽  
L. Schüler
Keyword(s):  
Animal Model ◽  
Body Weight ◽  
Egg Production ◽  
Additive Model ◽  
The Body ◽  
Phenotypic Variance ◽  
Egg Weight ◽  
Term Selection ◽  
Inbreeding Coefficients

Abstract. This study estimates the additive and non-additive variances for egg production and body weight traits of two lines of quails from a long-term selection with the help of the REML method. For the body weight of 42-day-old females (BW42f) and males (BW42m), a total of 7,934 records for line 1 and 7,214 records for line 2 from 21 generations were used in our analyses. Additionally, 1,717 records of females from line 1 and 1,671 records of females from line 2 contained information on their egg production at an age of 42 to 200 days (EN200), on the average egg weight for the first 11 weeks of their laying season (EW1), on the average egg weight from weeks 12 to 23 (EW2), and on their body weight at an age of 200 days (BW200f). A multivariate additive animal model and one-trait dominance models, which include the inbreeding coefficients as covariates, were fitted to the data. The estimates of the heritability gained from our dominance models were smaller than those from the additive model. For line 1, the heritability values decreased for EN200 from 0.35 to 0.32, for EW1 from 0.66 to 0.56, for BW200f from 0.42 to 0.38, and for BW200m from 0.51 to 0.49, respectively. For the first line, the respective ratio (d2) of the dominance variance to the phenotypic variance for EN200, EW1, BW200f and BW200m was 0.08, 0.22, 0.09 and 0.21, and the values for the second line were 0.12, 0.06, 0.001 and 0.23.

scholarly journals Quantitative Trait Loci Mapping of Resistance to Sugarcane Mosaic Virus in Maize

1999 ◽  
Vol 89 (8) ◽  
pp. 660-667 ◽  
Author(s):  
Xianchun Xia ◽  
Albrecht E. Melchinger ◽  
Lissy Kuntze ◽  
Thomas Lübberstedt
Keyword(s):  
Quantitative Trait Loci ◽  
Mosaic Virus ◽  
Quantitative Trait ◽  
Virus Disease ◽  
Interval Mapping ◽  
Field Trials ◽  
Sugarcane Mosaic Virus ◽  
Phenotypic Variance ◽  
Environment Interaction ◽  
Trait Loci

Sugarcane mosaic virus (SCMV) is an important virus disease of maize (Zea mays) in Europe. In this study, we mapped and characterized quantitative trait loci (QTL) affecting resistance to SCMV in a maize population consisting of 219 F3 or immortalized F2 families from the cross of two European maize inbreds, D32 (resistant) × D145 (susceptible). Resistance was evaluated in replicated field trials across two environments under artificial inoculation. The method of composite interval mapping was employed for QTL detection with a linkage map based on 87 restriction fragment length polymorphism and 7 mapped microsatellite markers. Genotypic and genotype × environment interaction variances for SCMV resistance were highly significant in the population. Heritabilities ranged from 0.77 to 0.94 for disease scores recorded on seven consecutive dates. Five QTL for SCMV resistance were identified on chromosomes 1, 3, 5, 6, and 10 in the joint analyses. Two major QTL on chromosomes 3 and 6 were detected consistently in both environments. Significant epistatic effects were found among some of these QTL. A simultaneous fit with all QTL in the joint analyses explained between 70 and 77% of the phenotypic variance observed at various stages of plant development. Resistance to SCMV was correlated with plant height and days to anthesis.

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