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Published byMeredith Lambert Modified over 8 years ago
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Genes and Variation 17.1
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Genotypes and phenotypes in evolution Natural selection acts on phenotypes and does not directly on genes. Natural selection favors members of a population that are the most fit.
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How is evolution defined in genetic terms? Gene pool contains all the alleles of all the genes in a population. Allele frequency is the number of times an allele occurs in a gene pool, compared to the total number of alleles for the same gene in the pool. Evolution is defined by the change in the frequency of alleles in a population over time.
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Sources of genetic variation Mutations = genetic change Sexual reproduction – crossing over in meiosis Lateral gene transfer - bacteria
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What determines the number of phenotypes for a given trait? The number of phenotypes depends on how many genes or alleles control the trait: – Single gene trait –complete or incomplete dominance. – Multiple allele – blood types – Polygenic – skin color
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Human height example polygenic trait Hair line example single gene trait
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