Lec23_QuantGen - BioG1780 Evolution and Biodiversity...

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BioG1780 Fall 2010 Evolution and Biodiversity Today’s lecturer: Matt Hare Lecture 23: Oct 22, 2010 Natural Selection on Quantitative Traits READING: Chapter 9, all sections except 2 A. Quantitative traits 1. Traits exhibiting continuous phenotypic distributions normal (bell shaped) distribution, mean, variance 2. Traits determined by many independent loci 3. Traits influenced by the environment B. Selection on quantitative traits 1. Directional selection shifts mean, reduces variance 2. Stabilizing selection mean doesn’t change, reduces variance 3. Disruptive selection mean doesn’t change, variance increases C. Heritability 1. Phenotypic variance has genetic and environmental components; V P = V G + V E a. genetic variance in populations has additive and dominance components; V G = V A + V D b. V A is genetic variation among individuals stemming from simple additive allele effects c. V D is genetic variation among individuals from gene interactions such as dominance
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