Hardy-Weinberg Activity
Goal: Calculate allele and genotype frequencies with p + q = 1 and p² + 2pq + q² = 1, estimate how common carriers are, and use a chi-square test to decide whether a population is in equilibrium.
What to do
- Choose From recessive phenotype frequency q² and press “q² = 0.09”. Record p, q and 2pq.
- Press “Cystic fibrosis ≈ 1 in 2,500” and record the same values.
- Choose From observed genotype counts. Press “49 · 42 · 9 (fits)” and then “30 · 60 · 10 (heterozygote excess)”. Record p, q, 2pq and χ² for each.
Record your results
| Population | p | q | 2pq (carriers) | χ² (counts only) |
|---|---|---|---|---|
| q² = 0.09 | ||||
| Cystic fibrosis (q² = 1 in 2,500) | ||||
| Counts 49 · 42 · 9 | ||||
| Counts 30 · 60 · 10 |
Questions
In a population, 9% of individuals show a recessive trait. Show how to find q, p and the frequency of carriers.
Cystic fibrosis affects about 1 in 2,500 newborns of European ancestry. What fraction of people are carriers? Give it as “about 1 in …”.
Why are there so many more carriers of cystic fibrosis than people who have it?
For the counts 30 AA, 60 Aa and 10 aa, calculate p and the counts you would expect if the population were in equilibrium.
Use χ² to decide whether the 30 · 60 · 10 population is in Hardy-Weinberg equilibrium. What might cause the excess of heterozygotes?
List the five conditions for Hardy-Weinberg equilibrium. Which one does heterozygote advantage break?
Free from Biology Lab · thebiologylab.org · HS-LS3-3: Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population.