Population Genetics - Western Oregon University
Transcript of Population Genetics - Western Oregon University
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Population Genetics• Population Genetics• Hardy-Weinberg equilibrium• Microevolution • Mutation • Genetic Drift • Migration • Non-random mating • Natural selection• Heterozygote advantage
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Population Genetics
• Population• gene pool• allele frequency• polymorphism
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Determining allele frequency
• starch gel electrophoresis
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DNA Markers
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Hardy-Weinberg equilibrium
• gene and genotype frequency do not change due to sexual reproduction alone
• Five assumptions• large population • no selection • no mutation • no migration • random mating
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Hardy-Weinberg• allele frequency:
p + q = 1.0
• genotype frequency: p2 + 2pq + q2 = 1.0
determine if population is in HW equilibrium
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Multiple alleles
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Calculations
• recessive allele frequency
• heterozygote frequency
• sex-linked genes and allele frequency
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Heterozygotes
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Microevolution
• Change in allele frequencies
• 5 mechanisms• Which assumption not
valid?
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Mutation
• Mutation rate (µ): 10-5 to 10-6 per generation
• Pt = Poe-µt t= # of generations
• To reduce P by ½, if µ= 10-5 & Po =0.96• Requires 69,000 generations• Mutation source of genetic variation does not
really cause rapid evolutionary change
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Gene Flow• homogenizing force • calculate changes in
allele frequency due to migration
• ∆p = m(pm – po)• M= fraction of migrants
to original population• Pm= allele freq of
migrating population• Po= allele freq of
original population
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MigrationB allele of Blood types
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Genetic Drift
• small population • fixed alleles and
extinction
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Genetic Drift
• founder effect • bottleneck effect
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Non-Random Mating
• assortative mating • loss of heterozygotes• disassortative mating• Inbreeding
depression• Higher levels of
genetic diseases
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Natural selection
• Differential reproductive success
• Selection coefficient• Relative fitness of
genotypes
Complete selection against recessive
qn = qo/ (1+ nqo)
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Selection
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Calculating relative fitness
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Heterozygote advantage
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Heterozygote advantage
• Qeq = S1/ (S1 + S2)• Sickle cell anemia • balanced
polymorphism • Why is Hbs
maintained in the population?
• What happens in US to allele frequency?
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