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Phenotypic value

Figure 9.10 A hypothetical example of directional selection and response to selection. In the parental generation those individuals with a phenotypic value of 12.0 or greater are allowed to mate. The selection differential is s = 12.5 - 10.0 = 2.5. Random mating among this subset of the parental population produces a distribution of progeny phenotypic values with a mean value of 11.0. The response to selection is R = 11.0 - 10.0 = 1.0. The realized heritability is therefore h2 = 1.0/2.5 = 0.40. Response to selection is proportionate to the degree to which parental phenotypic values are caused by the phenotypic effects of alleles. Parental phenotypic values being caused by genotypes or the environment do not lead to response to selection since these causes of phenotypic value are not inherited by offspring.

Phenotypic value

Figure 9.10 A hypothetical example of directional selection and response to selection. In the parental generation those individuals with a phenotypic value of 12.0 or greater are allowed to mate. The selection differential is s = 12.5 - 10.0 = 2.5. Random mating among this subset of the parental population produces a distribution of progeny phenotypic values with a mean value of 11.0. The response to selection is R = 11.0 - 10.0 = 1.0. The realized heritability is therefore h2 = 1.0/2.5 = 0.40. Response to selection is proportionate to the degree to which parental phenotypic values are caused by the phenotypic effects of alleles. Parental phenotypic values being caused by genotypes or the environment do not lead to response to selection since these causes of phenotypic value are not inherited by offspring.

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