Learning Objective: At the end of this lesson, the learner will be able to describe the principles of population genetics, including genetic drift, natural selection, and bottleneck/founder effects, and apply these concepts to human evolution and disease allele frequencies.
High-Yield Concepts
| Concept | Description | Example / Notes |
|---|---|---|
| Bottleneck effect | A sudden reduction in population size causes random loss of alleles, changing allele frequencies by chance rather than selection | Natural disaster kills most individuals; the remaining population has different allele frequencies |
| Founder effect | A type of bottleneck caused by a small group separating from a larger population | A few colonizers establish a population; certain alleles become overrepresented |
| Natural selection | Alleles that increase fitness are more likely to be passed on; deleterious alleles are removed | Human evolution: sickle cell trait confers malaria resistance |
| Genetic drift | Random fluctuations in allele frequencies in a population, independent of fitness | Bottleneck and founder effects are examples, more pronounced in small populations |
High-Yield Tips
- Genetic drift is chance-driven, not selection-driven.
- Bottleneck effect → reduces genetic diversity.
- Founder effect → explains the high prevalence of certain genetic diseases in isolated populations (e.g., Tay-Sachs in Ashkenazi Jews).
- Natural selection → acts on fitness, increasing the frequency of advantageous alleles.
