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Questions and Answers
What does the study of population genetics primarily focus on?
What does the study of population genetics primarily focus on?
A gene is a DNA sequence that codes for a protein only.
A gene is a DNA sequence that codes for a protein only.
False (B)
What term describes a situation where a diploid organism has two identical alleles for a gene?
What term describes a situation where a diploid organism has two identical alleles for a gene?
homozygous
The observable characteristics of an individual are referred to as the ______.
The observable characteristics of an individual are referred to as the ______.
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Match the following terms with their descriptions:
Match the following terms with their descriptions:
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What is a polymorphic gene?
What is a polymorphic gene?
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A population's genetic composition never changes.
A population's genetic composition never changes.
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What is a single nucleotide polymorphism (SNP)?
What is a single nucleotide polymorphism (SNP)?
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Which of the following is NOT a factor that governs microevolution?
Which of the following is NOT a factor that governs microevolution?
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Natural selection leads to adaptations that decrease the survival and reproduction of a population.
Natural selection leads to adaptations that decrease the survival and reproduction of a population.
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What is the term for the likelihood of an individual contributing fertile offspring to the next generation?
What is the term for the likelihood of an individual contributing fertile offspring to the next generation?
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Allelic variation arises from ______ mutations.
Allelic variation arises from ______ mutations.
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Fitness, in the context of natural selection, is a measure of:
Fitness, in the context of natural selection, is a measure of:
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The mean fitness of a population decreases over time as natural selection occurs.
The mean fitness of a population decreases over time as natural selection occurs.
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What is the name of the pigment associated with the color red?
What is the name of the pigment associated with the color red?
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What process is responsible for beneficial traits becoming more common in successive generations?
What process is responsible for beneficial traits becoming more common in successive generations?
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The MC1R gene is responsible for the production of eumelanin.
The MC1R gene is responsible for the production of eumelanin.
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In a diploid population, how many copies of a given allele do homozygotes have?
In a diploid population, how many copies of a given allele do homozygotes have?
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In a population, allele and ______ frequencies can be used to analyze genetic variation.
In a population, allele and ______ frequencies can be used to analyze genetic variation.
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If the frequency of one allele is 0.3, and there are only two alleles, what is the frequency of the other allele?
If the frequency of one allele is 0.3, and there are only two alleles, what is the frequency of the other allele?
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Heterozygotes have two identical copies of a given allele.
Heterozygotes have two identical copies of a given allele.
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What is the name for a variant form of a gene?
What is the name for a variant form of a gene?
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Match the flower color with its associated genotype in four-o'clock plants:
Match the flower color with its associated genotype in four-o'clock plants:
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What do p² and q² represent in the Hardy-Weinberg equation?
What do p² and q² represent in the Hardy-Weinberg equation?
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The Hardy-Weinberg equation predicts that allele and genotype frequencies will always change from one generation to the next.
The Hardy-Weinberg equation predicts that allele and genotype frequencies will always change from one generation to the next.
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What does it indicate when researchers find that a population is not in Hardy-Weinberg equilibrium?
What does it indicate when researchers find that a population is not in Hardy-Weinberg equilibrium?
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In the Hardy-Weinberg equation, the term 2pq represents the genotype frequency of the ______
In the Hardy-Weinberg equation, the term 2pq represents the genotype frequency of the ______
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Match the following conditions with their effect on Hardy-Weinberg equilibrium:
Match the following conditions with their effect on Hardy-Weinberg equilibrium:
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Which of the following is NOT a condition for Hardy-Weinberg equilibrium?
Which of the following is NOT a condition for Hardy-Weinberg equilibrium?
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Microevolution describes large-scale evolutionary changes over geological time scales.
Microevolution describes large-scale evolutionary changes over geological time scales.
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Name two specific mechanisms that can introduce new genetic variation into a population.
Name two specific mechanisms that can introduce new genetic variation into a population.
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What is the fitness of the Aa genotype, given that AA produces 5 offspring, Aa produces 4 offspring, and aa produces 1 offspring?
What is the fitness of the Aa genotype, given that AA produces 5 offspring, Aa produces 4 offspring, and aa produces 1 offspring?
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Directional selection always leads to increased variation within a population
Directional selection always leads to increased variation within a population
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What type of selection favours individuals with intermediate phenotypes and selects against those with extreme phenotypes?
What type of selection favours individuals with intermediate phenotypes and selects against those with extreme phenotypes?
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_______ selection maintains genetic diversity in a population over many generations.
_______ selection maintains genetic diversity in a population over many generations.
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In diversifying selection, what is the most likely environment for this type of selection to occur?
In diversifying selection, what is the most likely environment for this type of selection to occur?
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In negative frequency-dependent selection, the fitness of a genotype increases as its frequency becomes higher.
In negative frequency-dependent selection, the fitness of a genotype increases as its frequency becomes higher.
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What are the two main mechanisms of balancing selection mentioned?
What are the two main mechanisms of balancing selection mentioned?
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Match the selection type with its description:
Match the selection type with its description:
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Which of the following best describes sexual selection?
Which of the following best describes sexual selection?
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Intrasexual selection involves mate choice, primarily by females.
Intrasexual selection involves mate choice, primarily by females.
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Define the term 'sexual dimorphism'.
Define the term 'sexual dimorphism'.
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The ________ effect occurs when a small group of individuals separates from a larger population to establish a new colony.
The ________ effect occurs when a small group of individuals separates from a larger population to establish a new colony.
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What is the primary effect of migration on allele frequencies between populations?
What is the primary effect of migration on allele frequencies between populations?
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Genetic drift has a stronger effect in large populations.
Genetic drift has a stronger effect in large populations.
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What is the main consequence of the Bottleneck Effect on a population's genetic diversity?
What is the main consequence of the Bottleneck Effect on a population's genetic diversity?
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________ selection often results in showy characteristics in males.
________ selection often results in showy characteristics in males.
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What is the purpose of cryptic female choice?
What is the purpose of cryptic female choice?
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Flashcards
Population Genetics
Population Genetics
The study of how genes and genotypes change within a population over time.
Gene Pool
Gene Pool
All alleles for a specific gene in a population.
Polymorphism
Polymorphism
A genetic variation within a population where more than one allele exists for a specific gene, with each allele having a frequency greater than 1%.
SNPs (Single Nucleotide Polymorphisms)
SNPs (Single Nucleotide Polymorphisms)
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Genotype
Genotype
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Phenotype
Phenotype
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Natural Selection
Natural Selection
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Sexual Selection
Sexual Selection
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Allele
Allele
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Allele Frequency
Allele Frequency
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Genotype Frequency
Genotype Frequency
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Pheomelanin
Pheomelanin
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Reproductive Success
Reproductive Success
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Adaptations
Adaptations
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Allele Frequencies
Allele Frequencies
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Fitness
Fitness
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Mean Fitness
Mean Fitness
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Genetic Drift
Genetic Drift
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Migration
Migration
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Hardy-Weinberg Equation
Hardy-Weinberg Equation
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Hardy-Weinberg Equilibrium
Hardy-Weinberg Equilibrium
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Disequilibrium
Disequilibrium
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Directional Selection
Directional Selection
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Stabilizing Selection
Stabilizing Selection
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Microevolution
Microevolution
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Introduction of New Genetic Variation
Introduction of New Genetic Variation
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Diversifying Selection
Diversifying Selection
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Balancing Selection
Balancing Selection
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Mechanisms that Alter Prevalence of Alleles or Genotypes
Mechanisms that Alter Prevalence of Alleles or Genotypes
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Heterozygote Advantage
Heterozygote Advantage
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Violations of Hardy-Weinberg Equilibrium
Violations of Hardy-Weinberg Equilibrium
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Real-World Populations Rarely Achieve Equilibrium
Real-World Populations Rarely Achieve Equilibrium
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Negative Frequency-Dependent Selection
Negative Frequency-Dependent Selection
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Balanced Polymorphism
Balanced Polymorphism
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Sexual Dimorphism
Sexual Dimorphism
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Intrasexual Selection
Intrasexual Selection
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Intersexual Selection
Intersexual Selection
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Cryptic Female Choice
Cryptic Female Choice
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Bottleneck Effect
Bottleneck Effect
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Founder Effect
Founder Effect
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Migration (Gene Flow)
Migration (Gene Flow)
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Nonrandom Mating
Nonrandom Mating
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Study Notes
Population Genetics
- Population genetics studies genes and genotypes within a population.
- It merges natural selection, Mendelian inheritance, and modern molecular genetics.
- Population geneticists examine genetic variation within gene pools, how variation changes between generations, and explanations for this variation.
Key Concepts
- Genes in populations
- Natural selection
- Sexual selection
- Genetic drift
- Migration and non-random mating
Key Terminology
- Gene: A DNA sequence coding for RNA or protein; contributes to organism traits.
- Gene locus: The specific location of a gene on a chromosome.
- Allele: Different variants of a gene.
- Genotype: The combination of alleles for a specific gene (e.g., Tt).
- Homozygous: Having identical alleles for a gene (e.g., AA).
- Heterozygous: Having different alleles for a gene (e.g., Aa).
- Gene pool: All the alleles for every gene in a given population.
Genotype vs. Phenotype
- Genotype: The combination of alleles an organism possesses at a specific locus or several loci.
- Phenotype: The observable characteristics of an organism. (E.g., homozygous dominant = AA, heterozygous = Aa, homozygous recessive = aa)
Populations
- A group of individuals of the same species occupying the same environment, able to interbreed.
- Some species span wide geographic areas and are divided into smaller populations.
Genes Are Usually Polymorphic
- Many traits display variation (polymorphism) within a population.
- A polymorphic gene has two or more alleles, with an allele frequency greater than 1%.
- Most variation stems from single nucleotide polymorphisms (SNPs).
- Large, healthy populations show high genetic diversity.
Polymorphism in Horse Coat Colour
- Chestnut vs. black coat colour in horses (and many other species) is due to different alleles of the MC1R gene.
- This gene affects eumelanin (black) vs. pheomelanin (red) pigment accumulation.
Allele and Genotype Frequencies
- Allele frequency: The proportion of a specific allele in a population.
- Genotype frequency: The proportion of a specific genotype in a population.
Example: Four o'Clock Flower
- A population of 100 four o'clock plants has different flower colors based on genotypes.
- Genotypes (and corresponding numbers) include: CRCR (49), CRCW (42), CWCW (9).
Allele frequency calculation
- Frequency of CW = [(CRCW) + 2(CWCW)] / 2(CRCR) + 2(CRCW) + 2(CWCW)
Hardy-Weinberg Equilibrium
- A mathematical relationship between allele and genotype frequencies within a population.
- Under certain conditions, allele and genotype frequencies will not change between generations (equilibrium).
- Conditions including: no new mutations, no natural selection, large population size, no migration between populations, random mating.
Hardy-Weinberg Equilibrium Predictions
- p² and q² represent frequencies of homozygous genotypes.
- 2pq represents frequency of heterozygous genotypes.
- This equation assumes that no other evolutionary factors like mutations, natural selection, or genetic drift affect the population.
Microevolution
- Evolution of a population by changes in gene pool in successive generations.
- It includes mechanisms including mutation, gene duplication, horizontal gene transfer, natural selection, genetic drift, migration, and non-random mating.
Factors That Govern Microevolution
- New mutations introduce new alleles with varying traits.
- Gene duplication creates extra copies of genes.
- Horizontal gene transfer occurs when a gene from one species moves to another.
- Natural selection leads to the adaptation and survival of organisms based on traits.
- Genetic drift results in chance changes in allele frequencies that are prominent in small populations.
- Migration of individuals or alleles into or out of a population changes their frequencies.
- Non-random mating can influence the balance of genotypes in a population.
Natural Selection
- Beneficial heritable traits consistently become more common over successive generations.
- It results in increased fitness within a population.
- It has various patterns (directional, stabilizing, diversifying, balancing).
Reproductive Success
- The likelihood that a particular genotype will contribute to the next generation compared to other genotypes.
- It depends on a number of traits (influences survival and breeding).
Fitness
- The measure of reproductive success.
- It's not always connected to physical attributes alone.
- A genotype's fitness is relative to other genotypes' values within a population.
- Mean fitness measures the population's average reproductive success.
Fitness Example
- Example: A hypothetical gene with alleles A and a shows different reproductive success (AA = 5 offspring, Aa = 4 offspring, aa = 1 offspring).
Natural Selection Patterns
- Directional selection.
- Stabilizing selection.
- Disruptive/Diversifying selection.
- Balancing selection.
Directional Selection
- Selection for one extreme phenotype.
- Driven by environmental changes or introduction of novel, highly fit alleles.
- Can lead to genetic monomorphism.
Example: Directional Selection (Mice).
- Dark brown mice have higher fitness than light-colored mice in a dark forest environment leading to an increase in their frequency in the population.
Example: Directional selection (antibiotic resistance).
- Individuals resistant to antibiotics tend to survive and reproduce more frequently in populations exposed to antibiotics.
Stabilizing Selection
- Selection for intermediate phenotypes.
- Extreme phenotypes either don’t survive well enough or do not reproduce sufficiently.
- Example includes clutch size or birth weight in offspring
Diversifying Selection (Disruptive Selection)
- Selection for two or more extreme phenotypes.
- Population occupies two environments, and fitness values are high in one environment but low in the other and vice versa.
- Members of the population need to be able to interbreed.
Balancing Selection
- Selection that maintains genetic diversity.
- Two common mechanisms: heterozygote advantage and negative frequency-dependent selection.
Heterozygote Advantage(Balancing Selection)
- Heterozygotes exhibit higher fitness compared to homozygotes.
- Example: Sickle cell disease in malaria-prone areas.
Negative Frequency-dependent Selection (Balancing Selection)
- Rare genotypes possess higher fitness than the common ones.
- Example: Predator-prey relationships, where rare prey is less susceptible to predation.
Sexual Selection
- Individuals with certain traits are favored for reproductive success.
- Often influences males more than females.
- Traits related to mate attraction (secondary sex characteristics).
- Two types: intrasexual selection and intersexual selection
Sexual Dimorphism
- Significant difference in appearances between the two sexes in a species.
Intrasexual Selection
- Male-to-male competition for access to mates.
- Examples include horns in sheep or antlers in moose or enlarged claws in fiddler crabs .
Intersexual Selection
- Mate choice based on the characteristics of the male.
- Example: the brightly colored plumage of peacocks.
Cryptic Female Choice
- Females choose which male's sperm fertilizes eggs.
- This can lead to differential fertilization success for males.
The Cost of Reproduction
- Traits favored by sexual selection may decrease survival.
- The cost is higher if these traits make organisms more conspicuous to predators, which could reduce their fitness.
Genetic Drift
- Random changes in allele frequencies due to chance events, not fitness.
- Strongest in smaller populations.
- Can lead to loss or fixation of alleles.
Bottleneck Effect (Genetic Drift)
- Population size suddenly decreases, and survives but loses genetic diversity.
- Remaining individuals randomly determine the allele frequencies of the next population.
Founder Effect (Genetic Drift)
- A small group separates from a larger population and starts a new colony.
- Allele frequencies in the new population may differ significantly from the original one.
Gene Flow
- Transfer of alleles into or out of a population.
- Happens when individuals with different allele frequencies migrate between populations.
- Tends to reduce differences between populations and increase genetic diversity within a single population.
Non-random Mating
- Individuals choose mates based on genotype or phenotype.
- This can alter genotype frequency in populations.
- Two forms of non-random mating are assortative and disassortative.
Assortative Mating
- Individuals with similar phenotypes are more likely to mate and increase the proportion of homozygotes.
Disassortative Mating
- Individuals with dissimilar phenotypes are preferentially matched, resulting in increased heterozygosity.
Inbreeding
- Mating of genetically related individuals.
- Increases homozygosity and decreases heterozygosity potentially impacting populations' overall fitness.
Inbreeding Depression
- Reduced fitness in a population due to inbreeding.
- Occurs when offspring of close relatives have lower fitness than those not related.
Genetic Restoration of Populations
- Conservation strategies may aid populations that have gone through inbreeding depression and gene flow problems by introducing new alleles.
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Description
This quiz explores key concepts in population genetics, including gene types, alleles, and factors affecting microevolution. Test your understanding of terms like polymorphic gene, single nucleotide polymorphism, and the role of natural selection. Perfect for students learning about genetic variation and evolutionary processes.
