EvolutionMedium NEET PriorityClass 12
Genetic Drift
Definition
Genetic drift is the random change in allele frequencies in a population due to chance events, not natural selection. It has a stronger effect in small populations. Two types are founder effect (new population from few individuals) and bottleneck effect (population size drastically reduced).
Key Points for NEET
- 1Random, non-adaptive evolutionary mechanism
- 2More significant in small populations
- 3Can lead to loss of genetic variation
- 4Founder effect: new colony from few individuals
- 5Bottleneck effect: population drastically reduced
Example
Amish community having high frequency of Ellis-van Creveld syndrome due to founder effect
Asked in NEET
NEET 2022NEET 2021
Common Mistakes to Avoid
- ✗Confusing genetic drift (random, non-adaptive) with natural selection (non-random, adaptive)
- ✗Thinking genetic drift only removes alleles — it can also fix (increase to 100%) neutral alleles randomly
- ✗Mixing up founder effect (colonization) with bottleneck effect (population crash) — both reduce variation
Quick Revision Notes
- ⚡Genetic drift is strongest in small populations — large populations are buffered against random changes
- ⚡Founder effect: Amish community with high Ellis-van Creveld syndrome frequency (classic NEET example)
- ⚡Bottleneck effect: cheetah population crash → very low genetic diversity today
- ⚡Hardy-Weinberg equilibrium assumes NO genetic drift (requires large population) — drift violates this
Related Terms
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