The genotypes AA and Aa have the relative fitness 1…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The genotypes and have the relative fitness 1. The genotype has the relative fitness 0.5, so . The frequency of is before selection. Mating is random.
- What is the mean fitness of the population, ?
- What is the frequency of after one round of selection?
- By how much did fall?
Need a reminder? The key ideaShow
Stabilising selection favours the mean and narrows the curve. Directional selection moves the curve to one side. Disruptive selection favours both ends. When is selected against with a coefficient , the new frequency is . For it is .
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.
Given. , .
Plan. Find the mean fitness, then the new frequency.
Step 1. (a) The share is . Mean fitness: .
Step 2. (b) . New .
Step 3. (c) .
Answer: ; ; .
Check. The fall is smaller than for a lethal allele, where , so a milder selection gives a smaller change.
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