1-30 quantitative genetics

1-30 quantitative genetics - QUANTITATIVE GENETICS Klug...

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QUANTITATIVE GENETICS Klug chap. 24: pg. 599-610 -traits with a small number of discrete phenotypes show discontinuous variation -examples of traits that show more variation with a continuous range of phenotype that cannot be easily classified into distinct categories (i.e. height, weight) = continuous variation -continuous variation across a range of phenotypes is measured and described in quantitative terms, so it’s called quantitative inheritance -varying phenotypes result from input of genes at multiple loci quantitative traits = polygenic -the terms complex and multifactorial are used to describe traits where a range of phenotypes results from gene action and environmental influences 24.1 | Not All Polygenic Traits Show Continuous Variation -continuous quantitative traits: phenotypic variation can fall at any point along a scale of measurement Meristic traits: phenotypes are recorded by counting whole #s (i.e. # of seeds in a pod, # of eggs laid by a hen in a year) // these are quantitative traits but they don’t have an infinite range of phenotypes (b/c only whole numbers) Threshold traits : polygenic // freq. environmental factors affect the phenotypes, so they are multifactorial // have a small # of discrete phenotypic classes 24.2 | Quantitative Traits can be Explained in Mendelian Terms -Bateson and Yule proposed the multiple-factor or multiple-gene hypothesis in which many genes, each individually behaving in a Mendelian fashion, contribute to the phenotype in a cumulative
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This note was uploaded on 09/02/2009 for the course BIO 315H taught by Professor Payne during the Spring '08 term at University of Texas at Austin.

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1-30 quantitative genetics - QUANTITATIVE GENETICS Klug...

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