Eeb 120 - Lecture 6/7

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Population Genetics

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Define:

1. Population

2. Gene Pool

3. Genetic Variation: (Locus + Allele)

4. Genotype:

5. Phenotype:

6. Allele Frequency:

7. Genotype Frequency

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What are the 5 mechanisms of evolution? What do all these mechanisms do?

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What are the requirements for Hardy-Weinberg Equilibrium to be in effec

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To achieve the equilibrium five conditions must be met:**Population must be very large.**Population must be isolated from other populations (no immigration or emigration).**No mutations.**Random mating.**No natural selection (i.e. every individual has an equal chance of survival)

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Hardy Weinberg Equilibrium

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* Reminder that calculating allele frequencies ignores individuals. It's all about the gene pool of a population. In contrast, genotype frequencies are determined y how alleles are sorted into particular combinations in the individuals across a population.

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Conditions for HWE to be met?

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Whyexactlydo violations of Hardy Weinberg equilibrium result cause evolution to happen?

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A.theyalwayschange allele and/or genotype frequencies

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Example of how each HW assumption violation changes allele frequencies

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What is genetic drift?

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Despite being a completely random process, drift has two predictable qualities:

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What else to consider about Genetic Drift?

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Some other things toconsider:

•becausedrift is a random process, the direction& magnitude of change (increase/ decrease) in one generation has no influence on that in the next generation (imaginea drunk stumbling two steps left, thenthree right, then oneleft…)

•inthe absence of all other mechanisms of evolution, all alleles will become either fixedor lost eventually– themore time that passes, the more likelyany particular allele is fixed/ lost

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A. 15%

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Genetic Drift: Fly Evidence Example

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What are Bottlenecks?

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Northern Elephant Seals Bottleneck example

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What is the founder effect?

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Founder Effect Island Example

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Genetic Drift & Bottleneck & Founder Effect

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Natural Selection and Fitness

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*Fitness is how many individuals with a certain genotype pass onto the next generation

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Hardy Weinberg Equation

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Fitness and Genotypes

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E. Need more info

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A. Natural Selection

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Population Size Matters

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Antagonistic Pleitropy

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Experimental Evolution: Short generation time allows us to watch evolution happen

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B. Additive

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A. Fully Dominant

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Types of Allele Dominance

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Additive Alleles

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*Most likely to reach fixation

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Recessive Alleles

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*Rely on drift to slowly increase amount of recessive alleles until more common and goes rapidly to fixation

*Side note, selection acts on phenotype only

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Dominant Alleles

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*Least likely to reach fixation. Beneficial dominant allele hides recessive allele from selection.

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Mutation Selection Balance

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How to select for variation: Negative frequency-dependent selection

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Inbreeding, Inbreeding Depression

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Inbreeding: Identical by Descent, Inbreeding Coefficient

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Inbreeding Example

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Landscape Genetics

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Landscape Genetics of Sea Slugs

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