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BIOL 3046: Molecular evolution
Key terms:
Genetic drift
Mutation
Bottleneck
Founder effect
Sampling error
Substitution
Review material
Genetic drift (PopGen T4)
Fixation
Polymorphism
Founder effect speciation hypothesis
Review questions:
1. Explain how the relationship between genetic drift of allele frequencies
and binomial sampling of gametes.
2. What is the fate of polymorphism in a population of infinite size? What
about a population of finite size?
3. Consider two populations with the following census sizes: Popn1 = 50
and Popn2 = 5000. The number of individuals that reproduce each
generation for popn1 = 50 and for popn2 = 5. What is the magnitude of
genetic drift over time within these two populations? What is the
expected effect on genetic diversity as a function of time? Explain the
basis for any differences between these two populations?
4. Explain why Ne is actually a measure of the reproductive sample size.
5. What controls the rate of change in allele frequencies under genetic drift?
What determines the probability that an allele is ultimately fixed or lost?
Consider two populations each with the frequency of A allele = 0.5:
Popn1 has Ne = 100000, and popn2 has Ne = 100. What can you say
about the fate of the A allele over time? What can you say about how
long it will take?
6. Explain why inbreeding and genetic drift are not independent in natural
populations. What are the combined effects of inbreeding and drift?
7. What is the relationship between mutation, polymorphism and
substitution under genetic drift.
8. Comment on those aspects of genetic drift that are predictable and those
that are unpredictable.
9. Consider the genetic effects of a severe bottleneck on two species; one
species recovers with no difficulties while the other species exhibits
increased frequencies of individuals exhibiting deleterious recessive
traits. Explain how two species subjected to bottlenecks of the same
magnitude can be affected so differently.
Understand the “keynotes” for genetic drift.
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