Hardy-Weinberg Equilibrium Principle
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Questions and Answers

What is one of the main reasons we use the Hardy-Weinberg Equilibrium Principle?

  • To find the frequency of a specific genotype in a population
  • To test evolution against a null model (correct)
  • To prove that evolution occurs
  • To determine the exact number of alleles in a population

    • What is one of the assumptions of the Hardy-Weinberg Equilibrium Principle?

  • Infinitely large population size (correct)
  • Random genetic drift
  • Selection acts strongly on the population
  • Mutation rates are high

    • What can be predicted using the Hardy-Weinberg Equilibrium Principle, given the allele frequencies?

  • The exact number of offspring in the next generation
  • The mutation rate of a specific allele
  • The genotype frequencies in the next generation (correct)
  • The gene flow between two populations

    • What happens to the allele and genotype frequencies if the assumptions of the Hardy-Weinberg Equilibrium Principle are met?

    <p>They remain the same over time</p> Signup and view all the answers

    What is an example of a dominant trait in cats, as discussed in the context of the Hardy-Weinberg Equilibrium Principle?

    <p>Polydactyly with 6-7 toes per hand</p> Signup and view all the answers

    What is the name of the equation that describes the genotype frequencies in a population, according to the Hardy-Weinberg Equilibrium Principle?

    <p>(p + q)2 = 1</p> Signup and view all the answers

    What is the frequency of genotype AA in the given example?

    <p>0.36</p> Signup and view all the answers

    What is the condition for a population to be in Hardy-Weinberg Equilibrium?

    <p>Allele frequencies are in equilibrium</p> Signup and view all the answers

    What is the frequency of allele A in the next generation, given the example?

    <p>0.6</p> Signup and view all the answers

    What is the implication of a population being in Hardy-Weinberg Equilibrium?

    <p>The population will not evolve</p> Signup and view all the answers

    What is the formula for the frequency of genotype AB in the general case?

    <p>2pq</p> Signup and view all the answers

    What is the sum of the allele frequencies in a population?

    <p>1</p> Signup and view all the answers

    What is the conclusion about the genotype frequencies in a population in Hardy-Weinberg Equilibrium?

    <p>They are given by p2, 2pq, and q2</p> Signup and view all the answers

    What is the assumption about the population in the Hardy-Weinberg Equilibrium principle?

    <p>The population is in equilibrium</p> Signup and view all the answers

    What is evolution in terms of Hardy-Weinberg?

    <p>Change in allele frequencies over time</p> Signup and view all the answers

    What does Hardy-Weinberg equilibrium imply about a population?

    <p>The population is not evolving</p> Signup and view all the answers

    What statistical test is used to determine if a population is in Hardy-Weinberg equilibrium?

    <p>Chi-squared test</p> Signup and view all the answers

    What is the consequence of violating the 'no selection' assumption in Hardy-Weinberg equilibrium?

    <p>The conclusion of H-W equilibrium is violated</p> Signup and view all the answers

    What is a key requirement for the Hardy-Weinberg equations to be used?

    <p>Whole numbers must be used, not frequencies</p> Signup and view all the answers

    What is a consequence of random mating in a population?

    <p>The population will be in Hardy-Weinberg equilibrium</p> Signup and view all the answers

    Study Notes

    Hardy-Weinberg Equilibrium Principle

    • The Hardy-Weinberg Equilibrium Principle is used to show that evolution does not happen under certain conditions.
    • It provides a set of testable assumptions, and if any of these assumptions are violated, the conclusions do not hold.
    • It serves as a null model to test evolution against.

    Assumptions of Hardy-Weinberg

    • There is no selection, meaning all members contribute equally to the gene pool.
    • There is no mutation, meaning no new alleles are created.
    • There is no migration, meaning all alleles stay in the gene pool.
    • The population size is infinitely large, meaning no random events or genetic drift occur.
    • Mates are chosen randomly (panmixia).

    Why Use Hardy-Weinberg?

    • It allows for the prediction of genotype frequencies given allele frequencies.
    • Genotypes will approximate a binomial distribution after one generation of random mating.
    • If allele frequencies are known, genotype frequencies can be predicted.
    • Allele and genotype frequencies will not change as long as the assumptions are met.

    Dominance and Hardy-Weinberg

    • A simple phenotypic example of dominance is polydactyly in cats, caused by a variant of the Pd gene.
    • In a population of 100 cats, if 60 are polydactyl and 40 are normal, the genotype frequencies can be calculated using the Hardy-Weinberg Equilibrium Principle.

    Numerical Example

    • Using the Hardy-Weinberg Equilibrium Principle, the genotype frequencies can be calculated:
      • AA: 0.36
      • Aa: 0.48
      • aa: 0.16
    • The allele frequencies in the next generation can be calculated:
      • Frequency of A: 0.6
      • Frequency of a: 0.4

    General Case

    • A single locus with alleles A and B has three possible diploid genotypes: AA, AB, and BB.
    • The frequency of allele A is p, and the frequency of allele B is q, where p + q = 1.
    • The genotype frequencies can be calculated using the Hardy-Weinberg Equilibrium Principle:
      • AA: p²
      • AB: 2pq
      • BB: q²

    Conclusions

    • The allele frequencies in a population will not change, generation after generation.
    • If the allele frequencies in a population are given by p and q, the genotype frequencies will be given by p², 2pq, and q².
    • A population in Hardy-Weinberg Equilibrium is not evolving.

    Testing Hardy-Weinberg Equilibrium

    • The Chi-squared test is used to determine if the Hardy-Weinberg Equilibrium holds or is broken.
    • The test formula is: χ² = Σ((observed – expected)² / expected).
    • The degrees of freedom is 1, and critical values can be looked up online or in a statistics textbook.

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    Description

    This quiz covers the Hardy-Weinberg Equilibrium Principle, its assumptions, and its importance in understanding evolution. It explains why this principle is used and what happens when its assumptions are violated.

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