October 22 2010 - October 22 2010 Genetic Variation Todays...

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October 22 2010 Genetic Variation Today’s questions: Why are many quantitative traits normally distributed? Where does genetic variation come from? And why did sex evolve? Q1. Why has it been difficult to understand the genetic basis of human traits like mental illness, intelligence, and aspects of personality? I. Polygenic Inheritance: Why is variation in so many traits normally distributed? Basic assumptions of the model: 1. Many genes are involved in quantitative traits 2. The genes assort independently (they’re not linked; all on different chromosomes) 3. In a population, there are many alleles of each gene 4. The effects of each allele add together Q2. It turns out that most quantitative traits are due to the action of dozens of genes, that some of these genes have much larger effects than others, and that their effects may not be additive(there can be gene by gene interaction). Which conclusion from the simple model we just reviewed is still valid? *Quantitative variation in traits results from the action of many genes
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October 22 2010 - October 22 2010 Genetic Variation Todays...

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