Name the factor that disturbs the Hardy-Weinberg equilibrium in each case…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Name the factor that disturbs the Hardy-Weinberg equilibrium in each case.
- A storm kills 90 per cent of a small island population, and the survivors are a chance sample.
- Birds fly in from another island and breed with the local birds.
- A mistake in the copying of DNA makes a new allele.
- A predator eats pale beetles more often than dark ones.
- Crossing over makes chromosomes with new combinations of alleles.
Need a reminder? The key ideaShow
Count gene copies: each individual has two. The frequencies of two alleles add up to 1. At equilibrium the genotypes are . Start from the recessive trait, which shows . The five factors that disturb the equilibrium are gene flow, drift, mutation, recombination and selection.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Genetic drift. The survivors are a random sample of a small population.
Step 2. (b) Gene flow. Alleles move in with the migrants.
Step 3. (c) Mutation. A change in the DNA makes a new allele.
Step 4. (d) Natural selection. The two kinds of beetle differ in survival, so they leave different numbers of young.
Step 5. (e) Genetic recombination. The alleles are shuffled into new combinations.
Answer: (a) genetic drift; (b) gene flow; (c) mutation; (d) natural selection; (e) genetic recombination.
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