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7.5 Hardy-Weinberg Equilibrium: revision map

The subtopic in the middle and four tasks round it: label a diagram, complete a table, put a process in order and fill 8 gaps. Every box rests on a learning objective of the topic in the AP Biology course and exam description. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.

Unit 7 practice questionsThe whole Unit 7 map

Topic 7.5

Hardy-Weinberg Equilibrium

AP Biology · Unit 7 Natural SelectionName

7.5.AThe Hardy-Weinberg square

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  1. 1
  2. 2
  3. 3
  4. 4

7.5.ASolving a Hardy-Weinberg problem

Number the steps in order.

  1. Take its square root to get q.
  2. Use p² and 2pq to find the other genotype frequencies.
  3. Multiply by the population size to get numbers of individuals.
  4. Calculate p as 1 minus q.
  5. Find the frequency of the recessive phenotype, which equals q².
Topic 7.5Hardy-Weinberg Equilibrium

7.5.AA worked example

StepCalculationResult
4% of a population shows a recessive traitq² = 0.04
Allele frequency qq = √0.04
Allele frequency pp = 1 − 0.2
Carriers (heterozygotes)2pq = 2 × 0.8 × 0.2

The two equations: p + q = 1 for alleles, and p² + 2pq + q² = 1 for genotypes.

7.5.AThe conditions

The Hardy-Weinberg model describes a population that is not evolving, so allele frequencies stay the same from generation to generation. It needs: mating, a very large population (no drift), no gene flow, no mutation and no natural selection. No real population meets all five, so it is a baseline: if observed genotype frequencies differ from it, one or more of these conditions is not being met, and the population is evolving.

Word bank 0.20.320.8dominant allele frequencyheterozygoteshomozygous dominanthomozygous recessiverandom

Answer key

Every box on the sheet with its gaps filled in, as the subtopic reads in full.

  1. LabelThe Hardy-Weinberg square

    1. dominant allele frequency
    2. homozygous dominant
    3. heterozygotes
    4. homozygous recessive

  2. TableA worked example

    StepCalculationResult
    4% of a population shows a recessive traitq² = 0.04
    Allele frequency qq = √0.040.2
    Allele frequency pp = 1 − 0.20.8
    Carriers (heterozygotes)2pq = 2 × 0.8 × 0.20.32

    The two equations: p + q = 1 for alleles, and p² + 2pq + q² = 1 for genotypes.

  3. GapsThe conditions

    The Hardy-Weinberg model describes a population that is not evolving, so allele frequencies stay the same from generation to generation. It needs: random mating, a very large population (no drift), no gene flow, no mutation and no natural selection. No real population meets all five, so it is a baseline: if observed genotype frequencies differ from it, one or more of these conditions is not being met, and the population is evolving.

  4. OrderSolving a Hardy-Weinberg problem

    1. Find the frequency of the recessive phenotype, which equals q².
    2. Take its square root to get q.
    3. Calculate p as 1 minus q.
    4. Use p² and 2pq to find the other genotype frequencies.
    5. Multiply by the population size to get numbers of individuals.