Genetic drift and gene flow
Mechanisms of evolution · Biology
DNA double helix
Interactive 3DThe twisted ladder of life — A–T and G–C base pairs winding 10 per turn.
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Study notes
The cheetah's genetic uniformity — all cheetahs nearly identical — is a bottleneck's scar: ~10,000 years ago few survived, and drift fixed their genes; today inbreeding threatens them. Pingelap island's colour-blindness (10% vs 1 in 30,000 worldwide) is a founder effect — one carrier among the 20 survivors after a 1775 typhoon. Meanwhile, neighbouring human populations stay similar through gene flow — migration blending differences away.