En anglais

When gene pools stand still

Science · Genetics & Evolution · ages 17-18

Name ______________________ Date ____________

Which of these does the model assume?
- Populations stay tiny and isolated
- Mating is random across the population
- Selection favors one allele strongly in every generation
Which pair of equations describes the Hardy-Weinberg model?
- p plus q equals 1 with p squared plus 2pq plus q squared equals 1
- p times q equals 1 with p squared minus 2pq minus q squared equals 1
- p minus q equals 1 with 2p plus 2q equals 1
A population in Hardy-Weinberg equilibrium keeps the same allele frequencies across generations.
Circle one: True False
How do you count copies of allele A from genotype counts?
- Count every individual exactly once, regardless of genotype
- Count only the heterozygotes and ignore the rest
- Count each AA twice and each Aa once
In 100 plants there are 24 AA, 36 Aa and 40 aa. What is the frequency of allele A?
Answer: ______________
A small inbred group mates among relatives. Which assumptions break?
- Huge population size and random mating
- No mutation and no gene flow
- The equations themselves stop adding up
A population's allele frequencies change across generations. What can this show?
- The population has evolved at that gene
- The population is in perfect equilibrium
- The counting method must be wrong
In 400 people, 64 are affected by a fully recessive condition. Assuming Hardy-Weinberg conditions, what is the carrier frequency?
Answer: ______________

Answer key

For grown-ups. Fold this page away before handing over the rest.

Mating is random across the population · Random mating, huge size, and no selection are all on the assumptions list.
p plus q equals 1 with p squared plus 2pq plus q squared equals 1 · Allele frequencies sum to one, and the genotype mix follows from squaring that sum.
True · Unchanging frequencies define equilibrium, and they mean no evolution is happening at that gene.
Count each AA twice and each Aa once · Each AA individual carries two copies of A, each Aa carries one, and each aa carries none.
0.42 · A copies are 48 plus 36, which is 84 of 200 total alleles. The frequency of A is 84 divided by 200, or 0.42.
Huge population size and random mating · Small groups drift by luck and relatives pair nonrandomly, breaking two assumptions at once.
The population has evolved at that gene · A lasting change in allele frequency is evolution at that gene. It shows that the baseline is not holding, but it does not identify selection by itself.
0.48 · The affected frequency is q squared, so q squared is 64 divided by 400, or 0.16. Thus q is 0.4, p is 0.6, and 2pq is 0.48.