Read Alleles, Variation and Population Change
Track whether a process creates allele combinations, moves alleles, or changes genotype frequencies.
Population Genetics and Variation is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Generate variation and change gene pools
Recombination reshuffles alleles into new combinations. Gene flow occurs when migrants contribute alleles to another population, changing its gene pool. Genetic drift is random change, strongest in small populations.
Calculate Hardy–Weinberg frequencies
Do not mix genotype and allele effects
Non-random mating changes genotype frequencies directly, while gene flow and drift can change allele frequencies. Check what the stem specifically asks before selecting an evolutionary agent.
Compare allele and genotype frequencies
For a diploid population, p(A)=(2AA+Aa)/(2N) and q(a)=(2aa+Aa)/(2N). Equal allele frequencies do not guarantee equal genotype frequencies or equal heterozygosity; calculate each quantity separately before judging Hardy–Weinberg claims.
Hardy–Weinberg and genetic drift
Hardy–Weinberg equilibrium assumes a large population, random mating, and no selection, migration or mutation. In a small population, genetic drift changes allele frequencies randomly and can eliminate either allele.
larger effective population size and additional founders reduce drift.
Compare populations before assuming equilibrium
Calculate allele frequency before comparing genotype pattern.
Their genotype frequencies can still differ; equal allele frequencies do not prove Hardy–Weinberg equilibrium. Choose B and C.
OlympIQ exam lens
- ✓Recombination creates new allele combinations.
- ✓Gene flow moves alleles between populations.
- ✓Heterozygotes: 2pq.
- ✓Separate genotype-frequency effects from allele-frequency change.
- ✓Allele frequency counts two copies per homozygote and one per heterozygote.
- ✓Equal allele frequencies do not imply identical genotype distributions.
- ✓Equal allele frequencies can coexist with different genotype frequencies.
A change in genotype proportions is not automatically a change in allele frequency.
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