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University of Toronto Mississauga

Psychology

PSY352H5

Robert Gerlai

Winter

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Psy252 review 1. Define heritability using mathematical model and explain the scientific definition as well. Heritability is defined as the ratio of genotypic variance (Vg) to the phenotypic variance (Vp) of a particular trait. It can be defined using the following formula: 2 h = V G(V + E ) ,Gwhere V is tGe genetic variance and V is theE environmental variance and V = P + V E wherG V is the Phenotypic variance. Therefore, if genetic analysis found that heritability of losing an eye is 0% then it can be said that in a population 0% of the variation is in the population for this trait will be based on genetics. i.e. 100% of variation is based on the environment. 2. What does it mean when heritability is 0%? It means that 0% of the variability observed in a population is based on genetic factors that is to say 100% of the variability is due to environmental factors. This make sense, assuming that genetically all individuals are born with 2 eyes but due to some environmental effects some lose 1 eye or both. For ex: in a population, every year grade 3 kids have a snowball fight with each other, with half of them getting one eye knocked out. Genetically, they all had eyes but due to environmental effects half of them lost one eye. This means that the variability seen in the population for 3 grade for this trait is based on environmental effects not genetic factors. This implies that relative importance of genes for the trait of losing an eye is negligible as genetically everyone is born with eyes. However, the environmental effects on this trait determine the variability found in the population. Genetic variance (Vg) is zero because this trait is so important that natural selection has selected against any variation. 3. Give a real or hypothetical example where heritability equals 100%. Explain how this would be possible and what this would mean in terms of environmental and genetic effects. If we assume that the heritability of IQ is 100%( hypothetically) then, www.notesolution.com

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