This problem goes beyond the NEET syllabus, but A-Level and IB ask it…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
This problem goes beyond the NEET syllabus, but A-Level and IB ask it. In a population of breeding individuals, drift reduces the share of heterozygotes by the factor in each generation. Two populations start with the same share of heterozygotes. One has , and the other has . Mating is random and there is no selection.
- What share of the original heterozygosity is left after 20 generations in the population of 50?
- What share is left in the population of 500?
- Which population loses its variation faster?
Need a reminder? The key ideaShow
Gene flow: . A founder group of individuals has gene copies, and a rare allele is missing with the chance . Drift in a small population is strong, and it wears away the heterozygosity by a factor in each generation.
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 . Twenty generations.
Plan. Raise the factor to the power .
Step 1. (a) . , which is per cent.
Step 2. (b) . , which is per cent.
Step 3. (c) The population of loses per cent, and the population of loses only per cent. The small population loses its variation faster.
Answer: per cent; per cent; the smaller population.
Check. The loss per generation is about , ten times larger for the smaller population.
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