Hardy-Weinberg Equilibrium - AP Biology

1. What does the variable $p$ represent in the Hardy-Weinberg principle?

   The frequency of one allele of a gene in the population. By convention $p$ is often assigned to the dominant allele, and $q$ is the frequency of the other allele, so $p + q = 1$ for a two-allele gene.

2. What does the Hardy-Weinberg law predict about allele frequencies?

   They remain constant over generations. Frequencies stay stable when all equilibrium conditions are met.

3. What is the significance of the Hardy-Weinberg principle in biology?

   It provides a model for genetic variation in populations. Serves as a null hypothesis to detect evolutionary change.

4. What does it mean if a population is not in Hardy-Weinberg equilibrium?

   Evolution is occurring. Deviations indicate one or more evolutionary forces are acting.

5. What is the Hardy-Weinberg equation for genotype frequencies?

   $p^2 + 2pq + q^2 = 1$. Represents all possible genotype combinations from $(p+q)^2$ expansion.

6. What is the sum of allele frequencies in Hardy-Weinberg equilibrium?

   1. All possible alleles must account for 100% of the gene pool.

7. Calculate $p^2$ if $p = 0.7$.

   $p^2 = 0.49$. Square the allele frequency: $(0.7)^2 = 0.49$.

8. If $p = 0.8$, what is $q$ and what does it represent?

   $q = 0.2$, frequency of the recessive allele. Since $p + q = 1$, $q = 0.2$ and represents recessive allele frequency.

9. What happens to genotype frequencies under Hardy-Weinberg equilibrium?

   They remain constant over generations. Genotype proportions remain unchanged across generations.

10. Which Hardy–Weinberg condition makes genetic drift negligible in the ideal model?

    A very large (ideally infinite) population. In a very large population, random sampling effects on allele frequencies from one generation to the next become negligible.

11. Which Hardy–Weinberg condition excludes creation of new alleles by DNA change?

    No mutation at the locus. Mutation would introduce new alleles or convert one allele into another, changing allele frequencies.

12. What is the frequency of the recessive phenotype if $q^2 = 0.04$?

    0.04. The recessive phenotype frequency equals $q^2$.

13. Determine $q$ if the frequency of $aa$ is $0.25$.

    $q = 0.5$. Since $q^2 = 0.25$, then $q = \sqrt{0.25} = 0.5$.

14. If $q = 0.4$, what is the frequency of the homozygous recessive genotype?

    $q^2 = 0.16$. Square the allele frequency: $(0.4)^2 = 0.16$.

15. Determine the frequency of $AA$ if $p = 0.6$.

    $p^2 = 0.36$. Square the allele frequency: $(0.6)^2 = 0.36$.

16. Find $q^2$ if the recessive allele frequency is $0.2$.

    $q^2 = 0.04$. Square the allele frequency: $(0.2)^2 = 0.04$.

17. Find the frequency of the dominant phenotype if $p = 0.8$ and $q = 0.2$.

    0.96. Dominant phenotype = $p^2 + 2pq = 0.64 + 0.32 = 0.96$.

18. What is the sum of genotype frequencies in Hardy-Weinberg equilibrium?

    1. All possible genotypes must account for 100% of the population.

19. Find $2pq$ if $p = 0.8$ and $q = 0.2$.

    $2pq = 0.32$. Multiply: $2 \times 0.8 \times 0.2 = 0.32$.

20. If $p = 0.7$, what is the frequency of the recessive allele?

    $q = 0.3$. Since $p + q = 1$, then $q = 1 - 0.7 = 0.3$.

21. If $q = 0.3$, what is the frequency of the homozygous dominant genotype?

    $p^2 = 0.49$. If $q = 0.3$, then $p = 0.7$, so $p^2 = (0.7)^2 = 0.49$.

22. Which condition of Hardy-Weinberg equilibrium involves mate selection?

    Random mating. Assumes individuals choose mates regardless of their genotype.

23. What does the variable $q$ represent in the Hardy-Weinberg principle?

    Frequency of the recessive allele. $q$ is the proportion of recessive alleles in the gene pool.

24. Calculate the frequency of heterozygotes if $p = 0.5$ and $q = 0.5$.

    $2pq = 0.5$. Calculate: $2 \times 0.5 \times 0.5 = 0.5$.

25. What is the main assumption of the Hardy-Weinberg equilibrium model?

    No evolution occurs in the population. Equilibrium assumes no evolutionary forces change allele frequencies.

26. Identify the term for $2pq$ in the Hardy-Weinberg equation.

    Frequency of heterozygous genotype. $2pq$ represents individuals with one copy of each allele type.

27. State the Hardy-Weinberg equation for allele frequencies.

    $p + q = 1$. The two allele frequencies must sum to 1 in a two-allele system.

28. If $p = 0.6$, what is $q$ in a Hardy-Weinberg population?

    $q = 0.4$. Since $p + q = 1$, then $q = 1 - 0.6 = 0.4$.

29. State one reason why a population might deviate from Hardy-Weinberg equilibrium.

    Mutation. Changes in DNA can alter allele frequencies over time.

30. Identify the term for $q^2$ in the Hardy-Weinberg equation.

    Frequency of homozygous recessive genotype. $q^2$ represents individuals with two copies of the recessive allele.

31. Which Hardy–Weinberg condition excludes allele exchange between populations?

    No migration (gene flow). Individuals or gametes moving into or out of the population would add or remove alleles and could change allele frequencies.

32. Identify the term for $p^2$ in the Hardy-Weinberg equation.

    Frequency of homozygous dominant genotype. $p^2$ represents individuals with two copies of the dominant allele.

33. Which Hardy–Weinberg condition concerns how individuals choose reproductive partners?

    Random mating with respect to the locus. Mate choice must be independent of genotype at that locus; nonrandom mating such as inbreeding shifts genotype frequencies away from $p^2$, $2pq$ and $q^2$.

34. What is the result if a population is in Hardy-Weinberg equilibrium?

    Allele frequencies remain constant. No evolutionary forces act to change the genetic composition.

35. Which Hardy–Weinberg condition excludes genotype-dependent survival and reproductive success?

    No natural selection (equal fitness for all genotypes). If some genotypes survived or reproduced more than others, their alleles would increase in frequency.

36. Calculate $q^2$ if $q = 0.3$.

    $q^2 = 0.09$. Square the allele frequency: $(0.3)^2 = 0.09$.

37. In Hardy-Weinberg, what is the expected frequency of the $AA$ genotype?

    $p^2$. The frequency of homozygous dominant individuals.

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