VUBio110BSp'08-NatSelFitnessSpecialCases 11-POST

VUBio110BSp'08-NatSe - Sickle Cell the heterozygote advantage the stable polymorphism Selection against two homozygotes 2 selection coefficients(S1

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Sickle Cell – the heterozygote advantage – the stable polymorphism
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Selection against two homozygotes 2 selection coefficients (S 1 and S 2 )
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Calculating allele frequencies with stable polymorphism (equilibrium)
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Change in selection pressure change in population characteristics
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Frequency of trait can affect fitness Frequency dependent selection (FDS) Positive FDS selection favors the more common trait in population fitness increases with increased frequency leads to loss of variation Negative FDS selection favors the rare trait fitness increases with decreased frequency maintains variation in a sometime cyclical fashion
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Polymorphism maintained through FDS http://bio.research.ucsc.edu/~barrylab/classes/evolution/NS_H2.HTM
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Elderflower Orchid Keys to negative FDS “rewardless flowers” naïve pollinators Pollinators alternate between visiting purple and yellow flowers The rare morph is visited proportionately more
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This note was uploaded on 04/07/2008 for the course BSCI 110B taught by Professor Due during the Spring '08 term at Vanderbilt.

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VUBio110BSp'08-NatSe - Sickle Cell the heterozygote advantage the stable polymorphism Selection against two homozygotes 2 selection coefficients(S1

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