Non-linear selection response inDrosophila: a strategy for testing the rare-alleles model of quantitative genetic variability

Genetica ◽  
1997 ◽  
Vol 99 (1) ◽  
pp. 59-66 ◽  
Author(s):  
James W. Curtsinger ◽  
Ruan Ming
Keyword(s):  
Genetic Variability ◽  
Selection Response ◽  
Quantitative Genetic ◽  
Rare Alleles ◽  
Linear Selection ◽  
Non Linear

scholarly journals UNEQUAL CROSSING OVER AT THE rRNA TANDON AS A SOURCE OF QUANTITATIVE GENETIC VARIATION IN DROSOPHILA

Genetics ◽  
1980 ◽  
Vol 95 (3) ◽  
pp. 727-742 ◽  
Author(s):  
R Frankham ◽  
D A Briscoe ◽  
R K Nurthen
Keyword(s):  
Genetic Variation ◽  
Selection Response ◽  
Crossing Over ◽  
Wild Type ◽  
X Chromosomes ◽  
Unequal Crossing Over ◽  
Quantitative Genetic ◽  
Y Chromosomes ◽  
Homozygous Line ◽  
Minimum Estimate

ABSTRACT Abdominal bristle selection lines (three high and three low) and controls were founded from a marked homozygous line to measure the contribution of sex-linked "mutations" to selection response. Two of the low lines exhibited a period of rapid response to selection in females, but not in males. There were corresponding changes in female variance, in heritabilities in females, in the sex ratio (a deficiency of females) and in fitness, as well as the appearance of a mutant phenotype in females of one line. All of these changes were due to bb alleles (partial deficiencies for the rRNA tandon) in the X chromosomes of these lines, while the Y chromosomes remained wild-type bb+. We argue that the bb alleles arose by unequal crossing over in the rRNA tandon.—A prediction of this hypothesis is that further changes can occur in the rRNA tandon as selection is continued. This has now been shown to occur.—Our minimum estimate of the rate of occurrence of changes at the rRNA tandon is 3 × 10-4. As this is substantially higher than conventional mutation rates, the questions of the mechanisms and rates of origin of new quantitative genetic variation require careful re-examination.

Optimum linear selection indexes for multiple generation objectives with non-linear profit functions

1995 ◽  
Vol 61 (1) ◽  
pp. 165-175 ◽  
Author(s):  
J. C. M. Dekkers ◽  
P. V. Birke ◽  
J. P. Gibson
Keyword(s):  
Optimal Control ◽  
Net Present Value ◽  
Selection Index ◽  
Index Theory ◽  
Planning Horizon ◽  
Simultaneous Optimization ◽  
Linear Selection ◽  
Non Linear ◽  
Profit Functions ◽  
Selection Indexes

AbstractA method to obtain linear selection indexes that maximize objectives that involve average profit in one or more generations within a planning horizon based on non-linear profit functions, was derived through application of optimal control theory. The method involves simultaneous optimization of indexes for each generation in the planning horizon. Optimum linear indexes were found to be conform indexes derived from selection index theory, with economic values equal to a weighted sum of partial derivatives of the profit function at the trait means which result in each generation of the planning horizon. Numerical procedures to derive optimum indexes are presented. Methods and properties of alternative strategies for selection witli non-linear profit functions are illustrated for selection on egg weight and rate of lay in poultry. In the example, the additional benefit of selection indexes that maximize cumulative net present value of profit over a planning horizon of10 years was small relative to use of traditional selection procedures. Optimal indexes were also derived with a derivative-free non-linear programming optimizer, with identical results. The latter method also allows incorporation of additional constraints.Possible extensions of the optimal control methodology to address other problems related to optimization of selection over multiple generations are discussed.

Bite performance surfaces of three ecologically divergent Iguanidae lizards: relationships with lower jaw bones

2019 ◽  
Vol 127 (4) ◽  
pp. 810-825
Author(s):  
Monique Nouailhetas Simon ◽  
Renata Brandt ◽  
Tiana Kohlsdorf ◽  
Stevan J Arnold
Keyword(s):  
Biomechanical Model ◽  
Disruptive Selection ◽  
Head Shape ◽  
Linear Combinations ◽  
Mechanical Advantage ◽  
Jaw Bones ◽  
Correlational Selection ◽  
Lower Jaw ◽  
Linear Selection ◽  
Non Linear

Abstract Traits that interact to perform an ecologically relevant function are expected to be under multivariate non-linear selection. Using the lower jaw morphology as a biomechanical model, we test the hypothesis that lower jaw bones of lizards are subjected to stabilizing and correlational selection, associated with mechanical advantage and maximum bite force. We used three closely related tropidurine species that differ in size, head shape and microhabitat: Eurolophosaurus nanuzae, Tropidurus hispidus and Tropidurus semitaeniatus. We predicted a common pattern of correlational selection on bones that are part of in-levers or part of the out-lever of the lower jaw. The predicted pattern was found in E. nanuzae and T. hispidus, but this could not be shown to be statistically significant. For T. semitaeniatus, we found significant disruptive selection on a contrast involving the surangular, and also significant directional selection on linear combinations of traits in all species. The results indicate that the non-linear selection on lower jaw bones does not reflect an optimum to enhance mechanical advantage in all species. Divergent functional demands and specific ecological contexts of species seem relevant in shaping patterns of selection on morphology.

scholarly journals Genetic Variability And Selection Response To Heat Tolerance Through Membrane Thermostability In Spring Wheat (Triticum Aestivum L)

1970 ◽  
Vol 23 (2) ◽  
pp. 15-22
Author(s):  
NCD Barma ◽  
MA Islam ◽  
MA Hakim ◽  
DKR Sarker
Keyword(s):  
Genetic Variability ◽  
Heat Tolerance ◽  
Selection Response ◽  
Research Centre ◽  
Direct Selection ◽  
Realized Heritability ◽  
Response To Selection ◽  
Early Generation ◽  
Membrane Thermostability ◽  
Selection For

The present investigation was undertaken to study the genetic variability and selection response of heat tolerance measured through membrane thermostability (MTS) in F2 derived F4 and F5 generations of five wheat crosses: Kanchan × Gourab, Gourab × Fang 60, Kanchan × Pavon 76, Gourab × Pavon76 and Fang 60 × Pavon76. Each cross was consisted of 65, 60, 77, 72 and 64 F4 bulks including two parents. The study was conducted both in the field and laboratory of Wheat Research Centre, Dinajpur during 2002-03 and 2003-04. A completely randomized design for laboratory experiment and randomized complete block design for field experiments was followed with three replications. Acquired thermal tolerance through Membrane Thermo-stability assay was performed in controlled environment as per method described by Ibrahim and Quick (2001). Other morpho-physiological traits were measured from field experiment. The crosses Kanchan × Gourab, Kanchan × Pavon 76 and Fang 60 × Pavon76 showed high genetic variability with high population mean for MTS in F4 bulks. These crosses also exhibited high-observed response to selection, realized heritability and heritability in standard unit indicating expected good gain through early generation selection. Direct response to selection for this trait was significant in these crosses in F5 generation. Direct selection for MTS significantly improved biomass, grain yield, thousand grain weight, grain filling rate and canopy temperature depression in crosses Kanchan × Pavon 76, Gourab × Pavon76 and Fang 60 × Pavon76 with few exceptions. Direct selection of MTS also improved chlorophyll retention at 21 days after anthesis in crosses Gourab × Fang 60 and Gourab × Pavon76. Significant intergeneration correlations (F4 vs. F5) were observed for MTS in all five crosses studied indicating possibility of effective improvement of this trait through selection in early generation.   Key words: Membrane thermostability; selection response; realized heritability; intergeneration correlation.DOI: http://dx.doi.org/10.3329/bjpbg.v23i2.9320 Bangladesh J. Pl. Breed. Genet., 23(2): 15-22, 2010

Testing quantitative genetic selection theory with the mouse: A review

2005 ◽  
Vol 2005 ◽  
pp. 238-238
Author(s):  
E. J. Eisen
Keyword(s):  
Genetic Selection ◽  
Selection Response ◽  
Farm Animals ◽  
Base Population ◽  
Selection Theory ◽  
Quantitative Genetic ◽  
Selection Experiments ◽  
Downward Bias ◽  
Dynamic Population ◽  
Good Agreement

The theory of quantitative genetics is used to predict certain outcomes in a dynamic population undergoing selection. The goal of this review is to demonstrate the value of the mouse as a model to test quantitative genetic selection theory.Heritablity estimates in a base population are used to predict selection response. How good is this prediction? Sheridan (1988) reported discrepancies between predicted and realized heritabilities in selection experiments with laboratory and farm animals. An updated summary of single-trait selection experiments for different traits in mice indicates good agreement between predicted and realized heritabilities (r = 0.81, P < 0.01), with no suggestion of upward or downward bias in the base estimates (Eisen, 2005).

scholarly journals Genetic Components of Variation in Nemophila menziesii Undergoing Inbreeding: Morphology and Flowering Time

Genetics ◽  
1998 ◽  
Vol 150 (4) ◽  
pp. 1649-1661 ◽  
Author(s):  
Ruth G Shaw ◽  
Diane L Byers ◽  
Frank H Shaw
Keyword(s):  
Flowering Time ◽  
Inbreeding Depression ◽  
Genetic Parameters ◽  
Random Mating ◽  
Selection Response ◽  
Phenotypic Variance ◽  
Genetic Components ◽  
Quantitative Genetic ◽  
Nemophila Menziesii ◽  
Quantitative Genetic Parameters

Abstract The standard approaches to estimation of quantitative genetic parameters and prediction of response to selection on quantitative traits are based on theory derived for populations undergoing random mating. Many studies demonstrate, however, that mating systems in natural populations often involve inbreeding in various degrees (i.e., self matings and matings between relatives). Here we apply theory developed for estimating quantitative genetic parameters for partially inbreeding populations to a population of Nemophila menziesii recently obtained from nature and experimentally inbred. Two measures of overall plant size and two of floral size expressed highly significant inbreeding depression. Of three dominance components of phenotypic variance that are defined under partial inbreeding, one was found to contribute significantly to phenotypic variance in flower size and flowering time, while the remaining two components contributed only negligibly to variation in each of the five traits considered. Computer simulations investigating selection response under the more complete genetic model for populations undergoing mixed mating indicate that, for parameter values estimated in this study, selection response can be substantially slowed relative to predictions for a random mating population. Moreover, inbreeding depression alone does not generally account for the reduction in selection response.

scholarly journals A New Viewpoint on Genetic Diversity in Prestice Black-Pied Pig: Did the Breed Suffer from a Bottleneck?

2020 ◽  
Vol 68 (2) ◽  
pp. 305-309
Author(s):  
Lenka Falková ◽  
Irena Vrtková ◽  
Štěpán Vrtek
Keyword(s):  
Genetic Diversity ◽  
Genetic Variability ◽  
Short Tandem Repeats ◽  
Tandem Repeats ◽  
Genetic Resource ◽  
Heterozygosity Excess ◽  
Rare Alleles ◽  
Recent Bottleneck ◽  
Short Tandem

The research was aimed at determination of genetic variability of Prestice Black-Pied (PC) pig breed (Czech national breed and genetic resource) and to evaluate possible presence of recent bottleneck in this closed small pig population. One hundred and eighty of breeding boars were analysed by eleven tetramer Short Tandem Repeats (STR) panel specifically developed for the genotyping of breeding livestock. Despite the fact that appearance of rare alleles, which may be relatively increased after recent bottleneck, was discovered, the heterozygosity excess was not significant. The PC breed has not undergone recent bottleneck and remained at mutation-drift equilibrium.

scholarly journals Improving the Efficiency of Artificial Selection: More Selection Pressure With Less Inbreeding

Genetics ◽  
1999 ◽  
Vol 151 (3) ◽  
pp. 1103-1114
Author(s):  
Leopoldo Sanchez ◽  
Miguel Angel Toro ◽  
Carlos García
Keyword(s):  
Genetic Variability ◽  
Mate Selection ◽  
Selection Pressure ◽  
Phenotypic Selection ◽  
Selection Response ◽  
Selection Differential ◽  
Genetic Progress ◽  
Selection Scheme ◽  
Real Population ◽  
Mean And Variance

Abstract The use of population genetic variability in present-day selection schemes can be improved to reduce inbreeding rate and inbreeding depression without impairing genetic progress. We performed an experiment with Drosophila melanogaster to test mate selection, an optimizing method that uses linear programming to maximize the selection differential applied while at the same time respecting a restriction on the increase in inbreeding expected in the next generation. Previous studies about mate selection used computer simulation on simple additive genetic models, and no experiment with a real character in a real population had been carried out. After six selection generations, the optimized lines showed an increase in cumulated phenotypic selection differential of 10.76%, and at the same time, a reduction of 19.91 and 60.47% in inbreeding coefficient mean and variance, respectively. The increased selection pressure would bring greater selection response, and in fact, the observed change in the selected trait was on average 31.03% greater in the optimized lines. These improvements in the selection scheme were not made at the expense of the long-term expectations of genetic variability in the population, as these expectations were very similar for both mate selection and conventionally selected lines in our experiment.

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