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week 5 prob session notes

week 5 prob session notes - Week 5 Quantitative Population...

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Week 5: Quantitative & Population Genetics Page 1 of 10 Fall 2009 Week 5 – Quantitative & Population Genetics Qualitative vs. Quantitative ٠ Characters of kind ٠ Characters of degree ٠ Discontinuous variation ٠ Continuous variation (discrete phenotypic classes) (phenotypic measurements form a spectrum) ٠ Single-gene effects ٠ Polygenic control ٠ Individual matings and many ٠ Population of organisms with their progeny mating possibilities required to analyze ٠ Analysis involves counts and ratios ٠ Analysis involves statistical estimates of population parameters (i.e. mean, standard deviation, etc.) In order for a trait to be quantitative, it must be: - Quantitative Measurement - Measurement of an Individual - Shows Variability in the Population - Has Unknown Genetics/Environment - Ignores Ordinal and Qualitative Traits Quantitative traits are controlled by multiple genes, each segregating according to Mendel's laws. These traits can also be affected by the environment to varying degrees. Questions Studied in Quantitative Genetics 1. What is the genetic and environmental contribution to the phenotype? 2. How many genes influence the trait? 3. Are the contributions of the genes equal? 4. How do alleles at different loci interact: additively? epistatically? 5. How rapid will the trait change under selection? HERITABILITY Key Terms H 2 Broad Sense Heritability h 2 Narrow Sense Heritability V(P) Phenotypic Variation V(G) Genotypic Variation V(E) Environmental Variation V(A) Additive Genetic Variation V(D) Non-Additive Genetic Variation
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