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Questions and Answers
In a population that meets the conditions for Hardy-Weinberg equilibrium, what is the primary implication for allele frequencies?
In a population that meets the conditions for Hardy-Weinberg equilibrium, what is the primary implication for allele frequencies?
- Allele frequencies will fluctuate randomly due to genetic drift.
- Allele frequencies will shift to eliminate less fit alleles.
- Allele frequencies will remain constant from one generation to the next in the absence of selection, mutation, drift, or migration. (correct)
- Allele frequencies will change predictably due to natural selection.
Which of the following scenarios accurately describes the founder effect?
Which of the following scenarios accurately describes the founder effect?
- A few individuals colonize a new, isolated area, leading to reduced genetic diversity. (correct)
- A large population experiences a sudden reduction in size due to a natural disaster.
- Migration between populations introduces new alleles, increasing genetic variation.
- A population's allele frequencies fluctuate randomly due to chance events.
What is the most accurate definition of fitness, in the context of natural selection?
What is the most accurate definition of fitness, in the context of natural selection?
- An individual's ability to survive in a given environment.
- The reproductive success of an individual with a particular phenotype. (correct)
- The physical strength and endurance of an individual.
- The number of offspring an individual can produce, regardless of their survival.
In a population of birds, larger beaks are favored during a drought because they can crack larger seeds. However, when rainfall is plentiful, birds with smaller beaks are more efficient at consuming the abundant small seeds. What type of selection is described?
In a population of birds, larger beaks are favored during a drought because they can crack larger seeds. However, when rainfall is plentiful, birds with smaller beaks are more efficient at consuming the abundant small seeds. What type of selection is described?
A mutation introduces a new allele into a population. While the allele is initially harmful, the environment changes, making the allele beneficial. What evolutionary mechanism is at play?
A mutation introduces a new allele into a population. While the allele is initially harmful, the environment changes, making the allele beneficial. What evolutionary mechanism is at play?
What is the primary effect of inbreeding on the genetic makeup of a population?
What is the primary effect of inbreeding on the genetic makeup of a population?
A gene affects both bone density and hair color. Alleles that increase bone density also cause lighter hair color and vice versa. This is an example of what?
A gene affects both bone density and hair color. Alleles that increase bone density also cause lighter hair color and vice versa. This is an example of what?
How does gene flow typically affect genetic differences between populations?
How does gene flow typically affect genetic differences between populations?
If the frequency of the recessive allele (q) for a trait is 0.2, calculate the frequency of the heterozygous genotype (2pq) assuming Hardy-Weinberg equilibrium.
If the frequency of the recessive allele (q) for a trait is 0.2, calculate the frequency of the heterozygous genotype (2pq) assuming Hardy-Weinberg equilibrium.
In a small, isolated population, a previously rare allele increases in frequency over several generations, not because it is advantageous, but simply by chance. What mechanism is most likely responsible for this change?
In a small, isolated population, a previously rare allele increases in frequency over several generations, not because it is advantageous, but simply by chance. What mechanism is most likely responsible for this change?
Flashcards
Population Genetics
Population Genetics
The study of allele distribution and frequency changes within populations over time.
Allele
Allele
Different versions of a gene at a specific locus.
Evolution
Evolution
Changes in allele frequencies from one generation to the next, indicating biological change.
Hardy-Weinberg Equilibrium
Hardy-Weinberg Equilibrium
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Genetic Drift
Genetic Drift
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Bottleneck Effect
Bottleneck Effect
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Founder Effect
Founder Effect
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Fitness
Fitness
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Natural Selection
Natural Selection
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Pleiotropy
Pleiotropy
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Study Notes
Population Genetics
- Defines the field as the study of allele distribution and frequencies within populations
- Examines how these allele frequencies change over time
- Alleles are different versions of a gene
- Evolution can be defined as the changes in allele frequencies from one generation to the next
Hardy-Weinberg Equilibrium
- Requires an infinite population size for equilibrium
- Assumes no fitness differences between genotypes
- Requires no mutation or migration
- Assumes random mating
- p²+2pq+q²=1, is the formula, also written p^2 + 2pq + q^2 = 1 and p2+2pq+q2=1
- p and q represent the frequencies of two alleles in the equation
- Serves as a null model predicting no evolutionary change without selection, mutation, drift, or migration
Genetic Drift
- Represents random changes in allele frequencies due to sampling error, especially in small populations
- Is more pronounced in small populations
- Can lead to the fixation or loss of alleles
- Genetic variation is reduced by bottlenecks and founder effects
- Bottleneck effect is a drastic reduction in population size leading to a non-representative set of alleles
- Founder effect involves a few individuals colonizing a new area, reducing genetic diversity in future populations
Fitness and Natural Selection
- Fitness is the reproductive success of an individual with a particular phenotype
- Components of fitness include survival to reproductive age and mating success
- Fecundity (offspring production) is a component of fitness
- Natural selection is differential survival and reproduction based on fitness differences between individuals
Selection Mechanisms
- Positive selection favors alleles that increase fitness
- Negative selection eliminates deleterious alleles
- Balancing selection maintains genetic diversity
- Negative frequency-dependent selection favors rare phenotypes
- Heterozygote advantage occurs when heterozygotes have a fitness advantage over homozygotes, like in sickle-cell anemia
Mutation
- Mutation is a source of new genetic variation in populations
- Mutation-selection balance is an equilibrium between the introduction of deleterious mutations and their removal by selection
Pleiotropy
- Pleiotropy is when a single gene affects multiple traits
- Antagonistic pleiotropy means a gene may have both beneficial and detrimental effects on fitness, depending on the environment
Population Subdivision
- Genetic drift in subdivided populations occurs due to barriers causing genetic divergence because of limited gene flow
- Gene flow is the movement of alleles between populations, which can counteract the effects of drift and subdivision
Inbreeding
- Inbreeding increases homozygosity, exposing recessive alleles to selection
- Inbreeding depression reduces fitness due to the expression of deleterious recessive alleles
Important Equations to Know
- Hardy-Weinberg Equation: p²+2pq+q²=1, where p + q = 1
- Change in Allele Frequency due to Selection: ∆p = p x (αA1/w)
- Ap = change in allele frequency due to selection
- p = frequency of the A1 allele
- α = average fitness of the population
- αA1 = average excess of fitness for the A1 allele
- Where ppp is the frequency of the A1 allele, aAlaA_1aA1 is the average excess fitness, and w is the average population fitness
Key Terms
- Alleles: Variants of a gene.
- Genetic Drift: Random fluctuation in allele frequencies.
- Bottleneck: Reduction in genetic diversity due to a sharp population decline.
- Founder Effect: Loss of genetic variation when a new colony is established by a small number of individuals.
- Fitness: Success in passing genes to the next generation.
- Pleiotropy: A gene affecting multiple traits.
- Gene Flow: Exchange of genes between populations.
- Inbreeding: Mating between closely related individuals.
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Description
Explore population genetics, the study of allele frequencies and their changes over time, with a focus on Hardy-Weinberg equilibrium. Understand how factors like population size, selection, mutation, and migration influence genetic variation. Learn the equation p²+2pq+q²=1 and its significance as a null model for predicting evolutionary change
