Genetic driftAQA A-Level Biology: Flashcards
What these 11 flashcards ask
- Define genetic drift.
- In which populations is genetic drift important?
- Why is drift important only in small populations?
- Does genetic drift depend on survival advantage?
- What can drift do to an allele in a small population?
- What is the effect of drift on genetic variation?
- Name the two forces affecting genetic variation in populations.
- How does drift differ from natural selection?
- Why is a population after a sudden fall in numbers likely to have different allele frequencies?
- A vole with 2 copies of an allele dies in a population of 50. What percentage of gene copies is lost?
- Why are populations with reduced variation more at risk?
Exam questions on Genetic drift
- A conservation biologist monitors a small island population of 12 flightless birds. A gene for feather pattern has two alleles, F and f, which have no effect on survival or reproduction. Over three generations the frequency of allele f changed from 0.50 to 0.29 and then to 0.00.Explain why the frequency of allele f fell to zero even though neither allele gave an advantage.2 marks
- Two isolated populations of voles carry the same gene with alleles Z and z, which have no effect on survival or reproduction. At the start, the frequency of allele Z is 0.50 in both populations. Population X has 50 voles and population Y has 5000 voles. After 20 generations the frequency of Z is 1.00 in population X and 0.49 in population Y.In each population, one vole with the genotype zz dies by chance. Calculate the percentage of all the copies of the gene lost from each population, and explain what this shows about genetic drift.2 marks
- A population of 2000 field mice lives in a meadow. A flood kills all but 10 of the mice. The deaths were not related to the phenotypes of the mice. The survivors then breed and the population recovers to 2000 mice.Explain how the flood could have changed the allele frequencies in the population that recovered.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).