geneticsexam2

geneticsexam2 - Quantitative genetic theory Model-fitting...

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Quantitative genetic theory: Model-fitting Basically: --Genetic similarity between organisms will lead to phenotype similarity if genes influence the trait being measured Methods allow us to: 1. Get estimates for genetic and environmental components of variance 2. Organize large amounts of data in meaningful ways in the form of models 3. Provide evidence that individual differences are an important result of evolution In humans: methods are not as direct and powerful as animal studies all models are still based on segregation at a single locus Additive Genetic Variation the additive affect of alleles phenotypic effect of the alleles is the mathematical sum of all alleles present for the trait since all alleles have an effect additive alleles produce predictable phenotypic scores in offspring: --the score of the offspring is just the average of the parental scores this gives us a prediction about the offspring that can be tested: --if the offspring score is NOT the average of the parental scores, we have evidence for non-additive action of the allele at a single locus, we have evidence of dominance deviation Non-additive Genetic Variation —the result of dominant alleles dominant alleles produce dominance deviation : = the difference between the expected additive genotypic score and the actual phenotypic score dominance produces unpredictable results for the scores of offspring offspring score depends on combination of alleles inherited and is NOT just an average of parental scores Polygenic Model
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additive variance (A) Genetic components dominance deviation G=A+D+I of variance (D) (G) epistasis interaction environment=E (I) Phenotypic values considered to be the sum of all genetic and environmental effects individual phenotypic scores are combined and phenotypic values are measured as deviations from the population mean for analysis, deviations from the mean are converted into variances phenotypic value= environmental effects + genetic effects + genotype/environment interaction effects variance components are now: V(P)=V(E)+V(G)+V(GxE)+2cov(G)(E) Inbred strains: V(G)=0 so, V(P)=V(E) humans: only less direct estimates possible from resemblance between relatives MZ twins: V(G)=0 and V(P)=V(E) Genotype x Environment interaction Main effects: --genotype and environment not independent --gene effects are modified by environment (and vice versa) --gene effects can be changed by certain environments --effects can be quite large
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Example liability to become a smoker
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This note was uploaded on 05/02/2010 for the course ANTH 1100 taught by Professor Stack,eile during the Fall '08 term at Colorado.

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geneticsexam2 - Quantitative genetic theory Model-fitting...

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