BIOB51H3 Lecture Notes - Lecture 18: Phenotypic Trait, Total Variation, Heritability
16 Apr 2016
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Document Summary
Qualitative traits: characteristics for which phenotypes fall into discrete categories. Quantitative traits: a characteristic for which phenotypes show continuous variation among individuals. traits determined by the environment and many mendelian genes. Focus on: phenotypes & heritability: statistical properties of population traits. Differences in lifetime reproductive success (intensity of selection) Effect of selection on phenotypic trait value(evolutionary response to selection) H2 heritability (extent to which parental phenotype predicts offspring phenotype) S selection differential (magnitude & direction of selection) Quantitative traits are always due to combined effect of genes and environment. Broad sense heritability: fraction of total variation in trait value that is due to variation in genes. Note: greater effect of variation in genes on variation in a trait (heritability) = stronger evolutionary response to selection. If there is a low heritability = strong environmental effect on trait variation = no evolutionary change. If there is a high heritability = strong genetic effect on trait variation = evolutionary change.
