A recessive allele a is lethal. Every aa individual dies before it can breed…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A recessive allele is lethal. Every individual dies before it can breed. In one generation the frequency of is . The survivors mate at random.
- What is in the next generation?
- What is one generation after that?
- What percentage of the babies of the second new generation is ?
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. and all die.
Plan. Apply twice. Then square the last value.
Step 1. (a) .
Step 2. (b) .
Step 3. (c) The babies are with the frequency , which is per cent. At the start the babies were , which is per cent.
Answer: ; ; per cent.
Check. The value of fell from to . The share of babies fell from per cent to about per cent. That is a bigger fall, because the share is the square of .
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