12_352 - L ectu re 1 2 : A s s o r t a t iv e M a t in g a...

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Lecture 12: Assortative Mating and Inbreeding Today s topics: 1. Random vs. nonrandom mating 2. Assortative mating vs. inbreeding 3. Inbreeding coefficient F 4. Estimating inbreeding 5. Effects of inbreeding Readings: Readings: 341-343 Random Mating The simple HW model assumes random mating . every individual has the same probability of mating with anyone, including themselves! Anything else = nonrandom mating Nonrandom mating occurs when mates are chosen by phenotype or genetic relatedness
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Nonrandom Mating Matings based on phenotype: 1. positive assortative mating: mate with the same phenotype more often than if you were choosing randomly 2. negative assortative mating: mate with the same phenotype less often … Matings based on genetic relatedness: 1. inbreeding: mate with relatives more often than if you were choosing randomly 2. Outbreeding: mate with relatives less often … Similarities Positive assortative mating similar to inbreeding because there are more homozygotes and fewer heterozygotes than under H–W. -> But the allele frequencies do not change! Both negative assortative mating and outbreeding lead to fewer homozygotes and more heterozygotes than under H–W.
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Differences between assort. mating and inbreeding a. Assort. mating only affects the mating trait; and it will strongly change genotype frequencies only if phenotype and genotype are closely related. b. Inbreeding and outbreeding affect all
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12_352 - L ectu re 1 2 : A s s o r t a t iv e M a t in g a...

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