Marker-assisted selection in an outbred poultry breeding nucleus

1996 ◽  
Vol 62 (1) ◽  
pp. 171-180 ◽  
Author(s):  
S. van der Beck ◽  
J. A. M. van Arendonk
Keyword(s):  
Genetic Variance ◽  
Genetic Model ◽  
Phenotypic Variance ◽  
Family Selection ◽  
Poultry Breeding ◽  
Cumulative Response ◽  
Trait Locus ◽  
Final Selection ◽  
Selection Of ◽  
Variance Explained

AbstractThe value of using a marker for a quantitative trait locus (QTL) affecting a sex-limited trait in an outbred poultry breeding nucleus was studied. Marker and QTL were in linkage equilibrium in the base population. The recombination rate between marker and QTL was 0-05. A closed nucleus with 9000 chickens per generation was deterministically simulated. The genetic model contained polygenes and a QTL linked to a marker. Genetic effects explained proportionately 0·3 of the phenotypic variance before selection. Under selection, polygenic variance reached an equilibrium and QTL variance decreased continuously over time. Cocks were selected in two steps. First the best cocks of each full-sib family were selected (within-family selection) while final selection took place after information on fiill-sibs was available. Hens were selected after they had completed production. The effect of using marker information in estimating breeding values was studied in an ongoing breeding programme. Transmission of marker alleles was always traceable. Cumulative response over five generations increased proportionately by 0·06 to 0·13 if a marker linked to a QTL that explained 0·2 of the genetic variance was used. Cumulative response increased up to 0·28 if the QTL explained 0-8 of the genetic variance. Additional response due to the use of a marker increased with increasing intensity of within-family selection of cocks, increased with increasing variance explained by the QTL and was higher if within-family selection of cocks was carried out after rather than before their sibs had complete records.

scholarly journals Marker assisted selection for genetic improvement of animal populations when a single QTL is marked

1995 ◽  
Vol 66 (1) ◽  
pp. 71-83 ◽  
Author(s):  
J. Ruane ◽  
J. J. Colleau
Keyword(s):  
Marker Assisted Selection ◽  
Genetic Variance ◽  
Genetic Model ◽  
Polymorphic Markers ◽  
Linkage Phase ◽  
Monte Carlo Simulation Study ◽  
Animal Populations ◽  
Single Character ◽  
Selection For ◽  
Trait Locus

SummaryA Monte Carlo simulation study to evaluate the benefits of marker assisted selection (MAS) in small populations with one marked bi-allelic quantitative trait locus (QTL) is described. In the base generation, linkage phase equilibrium between the markers, QTL and polygenes was assumed and frequencies of 0·5 for the two QTL alleles were used. Six discrete generations of selection for a single character measured on both sexes followed. An additive genetic model was used with the QTL positioned midway between two highly polymorphic markers. Schemes were simulated with a distance of 10 cM between the QTL and either of the two markers and with the QTL explaining 1/8 of the total genetic variance in the base generation. Values of 0·5, 0·25 or 0·1 were assumed for the heritability. Eight males and 16, 32 or 64 females were selected each generation with each dam producing four sons and four daughters as candidates for the next generation. Animals were evaluated with a conventional BLUP animal model or with a model using marker information. MAS resulted in substantially higher QTL responses (4–54%), especially with low heritabilities, than conventional BLUP but lower polygenic responses (up to 4%) so that the overall effect on the total genetic response, although in the majority of cases favourable, was relatively small. With QTLs of larger size (explaining 25% of the genetic variance) comparable results were found. When the distance between the QTL and the markers was reduced to 2 cM, genetic responses were increased very slightly with a heritability of 0·5 whereas with a heritability of 0·1 responses were increased by up to 10%, compared with conventional BLUP. Results emphasize that MAS should be most useful for lowly heritable traits and that once QTLs for such traits have been identified the search for closely linked polymorphic markers should be intensified.

scholarly journals A classical setting for associations between markers and loci affecting quantitative traits

1999 ◽  
Vol 74 (3) ◽  
pp. 271-277 ◽  
Author(s):  
DAHLIA M. NIELSEN ◽  
B. S. WEIR
Keyword(s):  
Genetic Marker ◽  
Quantitative Trait ◽  
Quantitative Traits ◽  
Genetic Variance ◽  
Genetic Model ◽  
Marker Locus ◽  
Multiple Alleles ◽  
Classical Setting ◽  
Tests Of Association ◽  
Trait Locus

We examine the relationships between a genetic marker and a locus affecting a quantitative trait by decomposing the genetic effects of the marker locus into additive and dominance effects under a classical genetic model. We discuss the structure of the associations between the marker and the trait locus, paying attention to non-random union of gametes, multiple alleles at the marker and trait loci, and non-additivity of allelic effects at the trait locus. We consider that this greater-than-usual level of generality leads to additional insights, in a way reminiscent of Cockerham's decomposition of genetic variance into five terms: three terms in addition to the usual additive and dominance terms. Using our framework, we examine several common tests of association between a marker and a trait.

scholarly journals Heritability is a poor, if not unhelpful, measure of complex human behavioral processes

2021 ◽  
Author(s):  
Agustin Fuentes ◽  
Kevin A Bird
Keyword(s):  
Human Behavior ◽  
Genetic Variance ◽  
Phenotypic Variance ◽  
Developmental Processes ◽  
Human Culture ◽  
Relative Contribution ◽  
Variance Explained

Heritability is not a measure of the relative contribution of nature vis-à-vis nurture, nor is it the phenotypic variance explained by or due to genetic variance. Heritability is a correlative value. The evolutionary and developmental processes associated with human culture challenge the use of ‘heritability’ for understanding human behavior.

scholarly journals Genetic variance for body size in a natural population of Drosophila buzzatii.

Genetics ◽  
1991 ◽  
Vol 128 (4) ◽  
pp. 739-750
Author(s):  
A Ruiz ◽  
M Santos ◽  
A Barbadilla ◽  
J E Quezada-Díaz ◽  
E Hasson ◽  
...  
Keyword(s):  
Genetic Variance ◽  
Genetic Model ◽  
Phenotypic Variance ◽  
Total Phenotypic Variance ◽  
Fourth Chromosome ◽  
Narrow Sense Heritability ◽  
Additive Variance ◽  
Thorax Length ◽  
Drosophila Buzzatii ◽  
F2 Generation

Abstract Previous work has shown thorax length to be under directional selection in the Drosophila buzzatii population of Carboneras. In order to predict the genetic consequences of natural selection, genetic variation for this trait was investigated in two ways. First, narrow sense heritability was estimated in the laboratory F2 generation of a sample of wild flies by means of the offspring-parent regression. A relatively high value, 0.59, was obtained. Because the phenotypic variance of wild flies was 7-9 times that of the flies raised in the laboratory, "natural" heritability may be estimated as one-seventh to one-ninth that value. Second, the contribution of the second and fourth chromosomes, which are polymorphic for paracentric inversions, to the genetic variance of thorax length was estimated in the field and in the laboratory. This was done with the assistance of a simple genetic model which shows that the variance among chromosome arrangements and the variance among karyotypes provide minimum estimates of the chromosome's contribution to the additive and genetic variances of the trait, respectively. In males raised under optimal conditions in the laboratory, the variance among second-chromosome karyotypes accounted for 11.43% of the total phenotypic variance and most of this variance was additive; by contrast, the contribution of the fourth chromosome was nonsignificant. The variance among second-chromosome karyotypes accounted for 1.56-1.78% of the total phenotypic variance in wild males and was nonsignificant in wild females. The variance among fourth chromosome karyotypes accounted for 0.14-3.48% of the total phenotypic variance in wild flies. At both chromosomes, the proportion of additive variance was higher in mating flies than in nonmating flies.

scholarly journals Genetic components of birth weight of texel sheep reared in extensive system

2017 ◽  
Vol 40 ◽  
pp. 36481
Author(s):  
Fernando Amarilho-Silveira ◽  
Nelson José Laurino Dionello ◽  
Gilson De Mendonça ◽  
Jaqueline Freitas Motta ◽  
Tiago Albandes Fernandes ◽  
...  
Keyword(s):  
Birth Weight ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Likelihood Method ◽  
Phenotypic Variance ◽  
Genetic Trend ◽  
Extensive System ◽  
Genetic Components ◽  
Best Fit ◽  
Variance Explained

This study aimed to estimate the components of (co)variance, genetic and phenotypic parameters and trends for birth weight. We used 783 birth weight records, between 2012 to 2016, of Texel sheep reared in extensive system. The components of (co)variance and the genetic parameters were estimated using six different animal models, using the restricted maximum likelihood method (REML). The model that best fit the data was Model 3, with estimates of direct additive genetic variance of 0.004, maternal permanent environment variance of 0.164, heritability coefficient of 0.011 and phenotypic variation attributed to the maternal permanent environment of 0.394. For the genetic trend, we observed a genetic gain of 0.413% and for the phenotypic trend, a phenotypic gain of 0.159 kg, between 2012 and 2016 were found. Estimates of direct heritability and proportion of the phenotypic variance explained by the maternal permanent environment presented lower and higher values, respectively, in comparison to other studies. For trends, both genetic and phenotypic, there were gains in birth weight between 2012 and 2016. 

scholarly journals Early Selection of Radiata Pine

2006 ◽  
Vol 55 (1-6) ◽  
pp. 182-191 ◽  
Author(s):  
C. A. Dean ◽  
P. P. Cotterill ◽  
R. D. Burdon
Keyword(s):  
Genetic Control ◽  
Genetic Variance ◽  
Genetic Correlations ◽  
Radiata Pine ◽  
Phenotypic Variance ◽  
Sectional Area ◽  
Growth Data ◽  
Additive Variance ◽  
Half Diallel ◽  
Selection Of

Abstract Additive genetic, dominance genetic and phenotypic variances and corresponding correlations were estimated for growth data collected from disconnected half-diallel progeny trials involving 25 Pinus radiata D. DON parents and replicated across two sites in central North Island, New Zealand. Sectional area of stem was measured at three, seven, 10 and 13 years after planting at both sites, and height at three and 10 years at one site. Sectional area at three years exhibited similar levels of estimated additive (σA2) and dominance (σD2) genetic variance. However, levels of σD2 remained approximately constant between three and 13 years while σA2 increased substantially. Thus, sectional-area growth changed from being under equal additive and dominance genetic control at three years to almost complete additive genetic control from seven to 13 years. The greater increase in additive variance relative to phenotypic variance led to increases in individual heritability from 0.16 to 0.28 to 0.35 for sectional-area increments between 3-7, 7-10 and 10-13 years, respectively. Height growth exhibited negligible levels of σD2 for the three- and 10-year measurements. The early sectional-area increment between 3-7 years showed an estimated additive genetic correlation of 0.87 with “mature” sectional area at 13 years. Subsequent sectional-area increments between 7-10 and 10-13 years showed estimates of additive genetic correlations of 0.99 with sectional area at 13 years. Dominance genetic correlations were much lower in magnitude, reflecting inconsistent dominance effects over time.

scholarly journals The Prediction of Selection Response in A Self-Fertilizing Species II. Family Selection

1969 ◽  
Vol 22 (5) ◽  
pp. 1245 ◽  
Author(s):  
DG Pederson
Keyword(s):  
Genetic Model ◽  
Selection Response ◽  
Single Locus ◽  
Complex Method ◽  
Family Selection ◽  
Locus Model ◽  
Unselected Population ◽  
Combined Selection ◽  
Change In Mean ◽  
Selection Of

The response to between-and within-family selection is considered for self-fertilizing populations. For a general genetic model involving m alleles at each of k loci the expected responses are written as the sum of (1) the natural change in mean due to decreasing heterozygosity, and (2) a component which is a function of the genetic and environmental variances within an unselected population. A single-locus model is then considered and the expected responses are written in terms of para-meters of the base population. General expressions are given for the ultimate response following relaxation of selection and these are interpreted in terms of the single-locus model. In the final section the efficiencies of the various methods are investigated. In general, within-family selection is relatively inefficient while between-family selection is usually to be preferred over the selection of individuals or the more complex method of combined selection.

scholarly journals Genetic parameters of soybean populations obtained from crosses between grain and food genotypes

2020 ◽  
Vol 43 ◽  
pp. e46968
Author(s):  
Cleber Vinicius Giaretta Azevedo ◽  
Bruno Henrique Pedroso Val ◽  
Lilian Cristina Andrade de Araújo ◽  
Ana Cristina Pinto Juhász ◽  
Antonio Orlando Di Mauro ◽  
...  
Keyword(s):  
Genetic Parameters ◽  
Genetic Variance ◽  
Agronomic Traits ◽  
Human Consumption ◽  
Phenotypic Variance ◽  
Consumer Market ◽  
Good Potential ◽  
Superior Genotypes ◽  
100 Seed Weight ◽  
Selection Of

 In addition to the agronomic traits of interest, soybean cultivars destined for human consumption must have specific attributes that meet the demands of the consumer market. To meet this demand, this study aimed to select progenies with agronomic and commercial traits of interest from soybean populations obtained from crosses between different food and grain genotypes and to estimate the genetic parameters of these populations. The F3:4 and F4:5 progenies that originated from the two crosses were evaluated in the 2015/16 and 2016/17 agricultural years, respectively, using the pedigree method. The experimental design utilized augmented blocks, while statistical analyses were performed by using the REML/BLUP methodology. The evaluated traits were plant height at maturity (APM), insertion height of first pod (AIV), lodging (AC), agronomic value (VA), number of pods per plant (NV), number of days to maturity (NDM), number of branches (NR), number of nodes (NN), 100-seed weight (PCS), and grain yield per plant (PG). The best progenies were selected, and the following genetic parameters were estimated: genetic variance, phenotypic variance, heritability, and selective accuracy. The estimates of the genetic parameters indicate the presence of high genetic variance in these populations. Heritability was high for most of the traits, indicating good potential for the selection of superior genotypes.

Measurements of the Cape Astrometric Survey of the Southern Hemisphere

1978 ◽  
Vol 48 ◽  
pp. 515-521
Author(s):  
W. Nicholson
Keyword(s):  
Southern Hemisphere ◽  
Automatic Measuring ◽  
Measuring Machine ◽  
Final Selection ◽  
Selection Of

SummaryA routine has been developed for the processing of the 5820 plates of the survey. The plates are measured on the automatic measuring machine, GALAXY, and the measures are subsequently processed by computer, to edit and then refer them to the SAO catalogue. A start has been made on measuring the plates, but the final selection of stars to be made is still a matter for discussion.

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.

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