**Genetic drift** is:
- Movement of genes due to natural selection
- Random fluctuation of allele frequencies in a population, especially significant in small populations
- Mutation rate in germ cells
- Migration of populations
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Correct answer: B. Random fluctuation of allele frequencies in a population, especially significant in small populations
Genetic drift is random (non-selective) change in allele frequency due to sampling variance — especially powerful in small populations.
The 'Sewall Wright effect'.
Can cause alleles to be fixed or lost purely by chance.