How do plant and animal breeders natureselect across

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How do plant and animal breeders (% nature)select across tens to hundreds of contributing genes simultaneously? This selection is based on a concept called Consider the variation in body size among people in this class What contributes to the variation? 1) Nutrition (environment) 2) Genes The proportion of the variation in body size that is due to differences in genotypes among individuals determines the heritability of the trait. heritability the proportion of the of phenotypic variation among individuals that is due to genetic variation among individuals and that causes offspring to resemble their parents How much of the phenotypic variation that we see is due to genetic variations vs. environmental variation? If all clones but reared in different environments all variation genetic 26 There is a small refinement of this definition for sexual organisms (concerning gene dominance and epistasis) that we will not not explore in this class Response to selection Time 0 1961 1999 3.5 7.0 Yield (tons) / Hectare wheat corn rice Consider the example of > 50 % INCREASE IN ONLY 40 YEARS most improvement was genetic & not environmental (not due to herbicides. fertilizer, etc.) Similar story for barley, soy beans, pigs, cattle, chickens, etc. Cereal grain production Evolution slow except with fast-generation species
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= h 2 If all phenotypic variation is genetic If all phenotypic variation is environmental G=1 to apply artificial selection for seed size, we will select and plant only the largest 10% only plant these seeds (= selected) relative number 0 average of selected G=0 0 900 average = 404 692 0 0 900 seed size (mg) ?
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