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Questions and Answers
In a population that deviates from Hardy-Weinberg Equilibrium (HWE) due to a single violated assumption, being able to predict the magnitude and direction of evolution requires knowing which of the following?
In a population that deviates from Hardy-Weinberg Equilibrium (HWE) due to a single violated assumption, being able to predict the magnitude and direction of evolution requires knowing which of the following?
- The mating preferences within the population.
- The selection strength and mutation rate. (correct)
- The specific migration patterns irrespective of genotype.
- The precise number of individuals lost to genetic drift.
The average fitness ($w_{avg}$) of a population is calculated using the equation $w_{avg} = p^2w_{11} + 2pqw_{12} + q^2w_{22}$. What key principle should one remember when utilizing this equation?
The average fitness ($w_{avg}$) of a population is calculated using the equation $w_{avg} = p^2w_{11} + 2pqw_{12} + q^2w_{22}$. What key principle should one remember when utilizing this equation?
- The w values represent relative fitness and do not need to sum to 1. (correct)
- This equation assumes that there is no mutation occurring in the population.
- The equation is only applicable when the population size is infinitely large.
- The values of w must always sum to 1, representing a complete distribution of fitness across the population.
In population genetics, what does $p = p/w_{avg}(pw_{11} + qw_{12} - w_{avg})$ represent?
In population genetics, what does $p = p/w_{avg}(pw_{11} + qw_{12} - w_{avg})$ represent?
- The change in allele frequency from one generation to the next. (correct)
- The selection coefficient of a particular allele.
- The rate of mutation in the population.
- The average fitness of the population after selection.
Why might a detrimental allele persist in a population despite its negative effects?
Why might a detrimental allele persist in a population despite its negative effects?
Which of the following is an example of directional selection?
Which of the following is an example of directional selection?
In an environment where heterozygotes (Aa) have a survival advantage over both homozygous dominant (AA) and homozygous recessive (aa) individuals, what is this phenomenon called?
In an environment where heterozygotes (Aa) have a survival advantage over both homozygous dominant (AA) and homozygous recessive (aa) individuals, what is this phenomenon called?
If $w_{11}$, $w_{12}$, and $w_{22}$ represent the relative fitnesses of the $A_1A_1$, $A_1A_2$, and $A_2A_2$ genotypes, respectively, what does the following equation $\hat{p} = \frac{w_{22} - w_{12}}{w_{11} - 2w_{12} + w_{22}}$ calculate?
If $w_{11}$, $w_{12}$, and $w_{22}$ represent the relative fitnesses of the $A_1A_1$, $A_1A_2$, and $A_2A_2$ genotypes, respectively, what does the following equation $\hat{p} = \frac{w_{22} - w_{12}}{w_{11} - 2w_{12} + w_{22}}$ calculate?
How does a diverse habitat contribute to the maintenance of multiple phenotypes in a population?
How does a diverse habitat contribute to the maintenance of multiple phenotypes in a population?
Which evolutionary force is most likely at play when specific flower colors become more common because bees learn to avoid the more frequent color, leading to rare colors having disproportionately high visitation rates?
Which evolutionary force is most likely at play when specific flower colors become more common because bees learn to avoid the more frequent color, leading to rare colors having disproportionately high visitation rates?
What is the role of physical proximity between genes on a chromosome in the context of maintaining a 'detrimental' allele?
What is the role of physical proximity between genes on a chromosome in the context of maintaining a 'detrimental' allele?
How does migration contribute to the persistence of detrimental alleles in certain regions?
How does migration contribute to the persistence of detrimental alleles in certain regions?
Given the formula for equilibrium, what is implied when the denominator is zero ($w_{11} - 2w_{12} + w_{22}$ = 0)?
Given the formula for equilibrium, what is implied when the denominator is zero ($w_{11} - 2w_{12} + w_{22}$ = 0)?
How effective would a single intervention (e.g., public health) need to be to shift a population past a least stable equilibrium?
How effective would a single intervention (e.g., public health) need to be to shift a population past a least stable equilibrium?
In a population of elderflower orchids, bees tend to visit less common flower colors. What would happen to color prevalence (more common vs. less common) if the bees did not 'learn' and kept visiting flower colors randomly?
In a population of elderflower orchids, bees tend to visit less common flower colors. What would happen to color prevalence (more common vs. less common) if the bees did not 'learn' and kept visiting flower colors randomly?
How can detrimental alleles lead to an advantage?
How can detrimental alleles lead to an advantage?
Flashcards
Mutation Rate
Mutation Rate
The rate at which new mutations occur in a population, affecting genetic diversity and evolution.
Selection Strength
Selection Strength
A measure of how well a genotype or phenotype contributes to the next generation, relative to other genotypes or phenotypes.
Average Fitness (w_avg)
Average Fitness (w_avg)
A metric that represents the average reproductive success of a population, calculated by combining the fitness values and frequencies of different genotypes.
Heterozygote Advantage
Heterozygote Advantage
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Heterozygote Disadvantage
Heterozygote Disadvantage
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Frequency-Dependent Selection
Frequency-Dependent Selection
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Why do 'Detrimental' Alleles Persist?
Why do 'Detrimental' Alleles Persist?
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Selection Patterns
Selection Patterns
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Study Notes
HWE Deviation
- If only one assumption of the Hardy-Weinberg equilibrium is violated, the magnitude and direction of evolution can be predicted.
- Magnitude and direction of evolution can be predicted by knowing: selection strength, mutation rate, migration numbers and genotypes, and mating preferences.
- Drift can affect evolution, but its magnitude can only be estimated.
Calculating Average Fitness
- The average fitness of a population can be calculated using the formula: Wavg = p^2w11 + 2pqw12 + q^2w22, where w values represent the fitness of each genotype.
- Wavg = average fitness of the population
- p = the frequency of allele 1
- q = the frequency of allele 2
- w11, w12, and w22 = fitness values for each genotype, respectively
- The w values in the average fitness equation do not need to add up to 1.
- The average fitness is the fitness of the population at a specific point in time, and each following generation has its own average fitness.
- Average fitness (wavg) is expected to increase each generation, with fitter alleles being passed on more frequently.
- Changes in selective pressures can alter the average fitness (wavg) of a population.
- The prediction of the direction and magnitude of allele frequency change is represented by Ap=p/wavg(pw11 + qw12 - wavg).
Why Detrimental Alleles Persist
- Mutations can recreate existing detrimental alleles.
- Detrimental alleles can persist, if the allele is simply nonfunctional and easy to replicate.
- Recessive detrimental alleles can stay hidden within a population.
- Many detrimental alleles are less functional or nonfunctional, but may not always be eliminated.
- Perfection in biology is unrealistic, as detrimental alleles may provide a benefit in certain circumstances.
- A1A2 heterozygotes may exhibit the highest fitness, even if A2A2 individuals are unfit.
- Chance events can influence the persistence of detrimental alleles.
Selection Patterns
- Directional selection favors one extreme phenotype over others.
- Differing alleles in a population may provide benefits through heterozygote advantage or disadvantage, and negative frequency dependent selection.
- A diverse habitat will results in multiple phenotypes being maintained.
- Migration between regions helps maintains "detrimental" alleles in a population.
- Allele Linkage can keep the "detrimental" allele in a population.
- Physical proximity between genes on a chromosome is only broken by chance.
- If a close allele is more advantageous than the "detrimental" allele it will be be maintained.
Heterozygote Advantage (Overdominance)
- Heterozygote advantage, also known as overdominance, occurs when heterozygotes have a higher fitness than either homozygote.
- Sickle-cell allele is seen more in areas that have high rates of malaria present.
- The most stable equilibrium value for p is calculated by:
- p = (w22 - w12) / (w11 - 2w12 + w22).
Heterozygote Disadvantage (Underdominance)
- The least stable equilibrium value for p is calculated by:
- p = (w22 - w12) / (w11 - 2w12 + w22)
- This uses the same equation as overdominance.
Frequency-Dependent Selection
- In elderflower orchids, bees will go to another color flower because the prior had no nectar, which effects finding nectar..
- The rare color flower has disproportionately high bee visits.
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Description
Explore how violating Hardy-Weinberg assumptions predicts evolution's magnitude and direction. Learn to calculate average population fitness using allele frequencies and genotype fitness values, noting its dynamic nature across generations. This also explains how natural selection, mutation, migration and genetic drift affect the magnitude and direction of evolution.
