The Nature of Quantitative Genetic Variation in Drosophila. II* Average Dominance of Abdominal Bristle Polygenes

A comparison of 13 abdominal bristle selection lines with their base population and with reciprocal Fls between the selection lines and the base population was carried out. There was no significant directional contribution of maternally inherited factors to selection response.

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

Genetics ◽

10.1093/genetics/95.3.727 ◽

1980 ◽

Vol 95 (3) ◽

pp. 727-742 ◽

Cited By ~ 1

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.

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Testing quantitative genetic selection theory with the mouse: A review

Proceedings of the British Society of Animal Science ◽

10.1017/s1752756200011492 ◽

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).

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Standing genetic variation as a major contributor to adaptation in the Virginia chicken lines selection experiment

10.1101/018721 ◽

2015 ◽

Cited By ~ 1

Author(s):

Zheya Sheng ◽

Mats E Pettersson ◽

Christa F Honaker ◽

Paul B Siegel ◽

Örjan Carlborg

Keyword(s):

Body Weight ◽

Genetic Variation ◽

Genetic Variance ◽

Additive Genetic Variance ◽

Selection Response ◽

Selective Sweeps ◽

Base Population ◽

A Genome ◽

Wide Scale ◽

Genomic Regions

Artificial selection has, for decades, provided a powerful approach to study the genetics of adaptation. Using selective-sweep mapping, it is possible to identify genomic regions in populations where the allele-frequencies have diverged during selection. To avoid misleading signatures of selection, it is necessary to show that a sweep has an effect on the selected trait before it can be considered adaptive. Here, we confirm candidate selective-sweeps on a genome-wide scale in one of the longest, on-going bi-directional selection experiments in vertebrates, the Virginia high and low body-weight selected chicken lines. The candidate selective-sweeps represent standing genetic variants originating from the common base-population. Using a deep-intercross between the selected lines, 16 of 99 evaluated regions were confirmed to contain adaptive selective-sweeps based on their association with the selected trait, 56-day body-weight. Although individual additive effects were small, the fixation for alternative alleles in the high and low body-weight lines across these loci contributed at least 40% of the divergence between them and about half of the additive genetic variance present within and between the lines after 40 generations of selection. The genetic variance contributed by the sweeps corresponds to about 85% of the additive genetic variance of the base-population, illustrating that these loci were major contributors to the realised selection-response. Thus, the gradual, continued, long- term selection response in the Virginia lines was likely due to a considerable standing genetic variation in a highly polygenic genetic architecture in the base-population with contributions from a steady release of selectable genetic variation from new mutations and epistasis throughout the course of selection.

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Quantitative genetic variation in body size of mice from new mutations.

Genetics ◽

10.1093/genetics/131.3.693 ◽

1992 ◽

Vol 131 (3) ◽

pp. 693-700 ◽

Cited By ~ 3

Author(s):

P D Keightley ◽

W G Hill

Keyword(s):

Genetic Variation ◽

Body Size ◽

Population Genetic ◽

Genetic Variance ◽

Genetic Component ◽

Confidence Limits ◽

Base Population ◽

Quantitative Genetic ◽

Better Than ◽

New Mutations

Abstract To measure the amount of new genetic variation in 6-week weight of mice arising each generation from mutation, selection lines derived from an initially inbred strain were maintained for 25 generations. An analysis using an animal model with restricted maximum likelihood was applied to estimate a mutational genetic component of variance for the infinitesimal model of many genes of small effect. Assuming that the inbred base population was at a mutation-drift equilibrium, it is estimated that the heritability for body size has increased by 1.0% per generation, with lower and upper confidence limits of 0.6% and 1.6%, respectively. A model which includes a mutational genetic component of variance fits the data much better than one involving only base population genetic variance. A model with no genetic component fits the data very poorly. An environmental covariance of body size of mother and offspring was included in the model and accounts for 10% of the variance. By using information only from the observed response to selection, the estimated increase in heritability from mutation is 0.3% per generation. These values are higher than published estimates for the increase in variance from spontaneous mutations in bristle traits of Drosophila, for which there are extensive data, but similar to estimates for various skeletal traits in mice.

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ESTIMASI NILAI HERITABILITAS BOBOT IKAN MAS VARIETAS PUNTEN DALAM PROGRAM SELEKSI INDIVIDU

Jurnal Riset Akuakultur ◽

10.15578/jra.11.3.2016.217-223 ◽

2016 ◽

Vol 11 (3) ◽

pp. 217

Author(s):

Estu Nugroho ◽

Budi Setyono ◽

Mochammad Su’eb ◽

Tri Heru Prihadi

Keyword(s):

Body Weight ◽

Selection Response ◽

Base Population ◽

Breeding Programs ◽

Male And Female ◽

Body Weight Trait ◽

Population Selection ◽

Selection For ◽

Weight Trait ◽

Selection Of

Program pemuliaan ikan mas varietas Punten dilakukan dengan seleksi individu terhadap karakter bobot ikan. Pembentukan populasi dasar untuk kegiatan seleksi dilakukan dengan memijahkan secara massal induk ikan mas yang terdiri atas 20 induk betina dan 21 induk jantan yang dikoleksi dari daerah Punten, Kepanjen (delapan betina dan enam jantan), Kediri (tujuh betina dan 12 jantan), Sragen (27 betina dan 10 jantan), dan Blitar (15 betina dan 11 jantan). Larva umur 10 hari dipelihara selama empat bulan. Selanjutnya dilakukan penjarangan sebesar 50% dan benih dipelihara selama 14 bulan untuk dilakukan seleksi dengan panduan hasil sampling 250 ekor individu setiap populasi. Seleksi terhadap calon induk dilakukan saat umur 18 bulan pada populasi jantan dan betina secara terpisah dengan memilih berdasarkan 10% bobot ikan yang terbaik. Calon induk yang terseleksi kemudian dipelihara hingga matang gonad, kemudian dipilih sebanyak 150 pasang dan dipijahkan secara massal. Didapatkan respons positif dari hasil seleksi berdasarkan bobot ikan, yaitu 49,89 g atau 3,66% (populasi ikan jantan) dan 168,47 g atau 11,43% (populasi ikan betina). Nilai heritabilitas untuk bobot ikan adalah 0,238 (jantan) dan 0,505 (betina).Punten carp breeding programs were carried out by individual selection for body weight trait. The base population for selection activities were conducted by mass breeding of parent consisted of 20 female and 21 male collected from area Punten, eight female and six male (Kepanjen), seven female and 12 male (Kediri), 27 female and 10 male (Sragen), 15 female and 11 male (Blitar). Larvae 10 days old reared for four moths. Then after spacing out 50% of total harvest, the offspring reared for 14 months for selection activity based on the sampling of 250 individual each population. Selection of broodstock candidates performed since 18 months age on male and female populations separately by selecting based on 10% of fish with best body weight. Candidates selected broodstocks were then maintained until mature. In oder to produce the next generation 150 pairs were sets and held for mass spawning. The results revealed that selection response were positive, 49.89 g (3.66%) for male and 168.47 (11.43%) for female. Heritability for body weight is 0.238 (male) and 0.505 (female).

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Maintenance of Quantitative Genetic Variation

10.1093/oso/9780198830870.003.0028 ◽

2018 ◽

Author(s):

Bruce Walsh ◽

Michael Lynch

Keyword(s):

Genetic Variation ◽

Quantitative Genetics ◽

Stabilizing Selection ◽

Quantitative Genetic ◽

Wide Range

One of the major unresolved issues in quantitative genetics is what accounts for the amount of standing genetic variation in traits. A wide range of models, all reviewed in this chapter, have been proposed, but none fit the data, either giving too much variation or too little apparent stabilizing selection.

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The Molecular Basis of Quantitative Genetic Variation in Central and Secondary Metabolism in Arabidopsis

Genetics ◽

10.1093/genetics/149.2.739 ◽

1998 ◽

Vol 149 (2) ◽

pp. 739-747 ◽

Cited By ~ 7

Author(s):

Thomas Mitchell-Olds ◽

Deana Pedersen

Keyword(s):

Enzyme Activity ◽

Genetic Variation ◽

Secondary Metabolism ◽

Genetic Correlations ◽

Theoretical Models ◽

Model Systems ◽

Activity Levels ◽

Significant Qtls ◽

Cis Acting ◽

Quantitative Genetic

Abstract To find the genes controlling quantitative variation, we need model systems where functional information on physiology, development, and gene regulation can guide evolutionary inferences. We mapped quantitative trait loci (QTLs) influencing quantitative levels of enzyme activity in primary and secondary metabolism in Arabidopsis. All 10 enzymes showed highly significant quantitative genetic variation. Strong positive genetic correlations were found among activity levels of 5 glycolytic enzymes, PGI, PGM, GPD, FBP, and G6P, suggesting that enzymes with closely related metabolic functions are coregulated. Significant QTLs were found influencing activity of most enzymes. Some enzyme activity QTLs mapped very close to known enzyme-encoding loci (e.g., hexokinase, PGI, and PGM). A hexokinase QTL is attributable to cis-acting regulatory variation at the AtHXK1 locus or a closely linked regulatory locus, rather than polypeptide sequence differences. We also found a QTL on chromosome IV that may be a joint regulator of GPD, PGI, and G6P activity. In addition, a QTL affecting PGM activity maps within 700 kb of the PGM-encoding locus. This QTL is predicted to alter starch biosynthesis by 3.4%, corresponding with theoretical models, suggesting that QTLs reflect pleiotropic effects of mutant alleles.

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