Lecture 14 - Lecture 14 Assumptions of Hardy Weinberg o...

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Lecture 14 Assumptions of Hardy Weinberg o Random mating o No mutation o No migration o No selection o Population is infinitely large (no chance events) o NO EVOLUTION – the frequency of alleles does not change over time Hardy Weinberg as a “null hypothesis” o If population is not in H-W equilibrium, then one of the assumption is being violated and evolution is occurring o Natural selection occurs if… There is consistent differences in fitness and/or reproductive success among phenotypes Phenotypic effects are heritable Natural Selection – differential survival and reproductive success o Does not have goal or purpose o Does NOT anticipate the future o In general, the average success of individuals increase over time o What happens to allele frequencies over time? Does genetic variation change? HOWEVER – it is not always the case that the “best” genotype increases and the “best” allele becomes fixed (heterozygote advantage…) In general, average success of individuals increase in a population Fitness – average reproductive success of a phenotype o Fitness is equivalent to the representation of phenotypes in the next generation o Depends on – genotype and environment (is genotype and environment specific) o Below – two genotypes with different per capita growth rates – Genotype B is more fit because it is more reproductively successful – it takes over and its genotype is fixed at 1
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o Fitness is environment specific Ex) Growth of spectinomyosin susceptible (wild-type) and resistant strains of Chlamydia bacteria No spectomyosin – wild type growth is faster With spectomyosin: growth of resistant strains is faster Therefore, different phenotypes become fixed in different environments o Box 12A – have a sense of how the model works Background o Alleles: A1 and A2 o Frequencies: p and q o Best genotype: w = 1 o w ij = measure of reproductive success
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This note was uploaded on 03/31/2008 for the course BIOEE 2780 taught by Professor Geber during the Fall '07 term at Cornell University (Engineering School).

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Lecture 14 - Lecture 14 Assumptions of Hardy Weinberg o...

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