Lecture Notes: Genetic Drift and Allele Frequencies

Introduction

• Halloween Candy Analogy
  • Comparing Halloween candy collection with genetic drift.
  • Personal preference for gummy bears.
  • Candy selection is a matter of chance, similar to genetic drift.

Genetic Drift

• Definition: Random changes in allele frequencies in a population.
• Comparison with Natural Selection:
  • Natural selection involves organisms with high fitness passing their alleles.
  • Genetic drift is not about fitness but chance.

Concepts and Effects

• The Bottleneck Effect

  • Imagined as a bottle with candy.
  • Shaking out a few candies doesn't represent the whole population.
  • Real-life example: natural disaster like a forest fire.
  • Survivors don't represent the original population, leading to new allele frequencies.

• The Founder Effect

  • Refers to organisms founding a new area.
  • The founders do not represent the original population.
  • Example: Seeds dispersed by wind to a new area.
  • The new population might not reflect the original genetic makeup.

Impact on Different Population Sizes

• Small vs. Large Populations
  • Genetic drift impacts small populations more significantly.
  • Fewer representatives increase the impact of random events.
  • Larger populations are less affected due to more genetic representation.

Conclusion

• Genetic drift is a mechanism for evolution, impacting allele frequencies.
• More profound effects are observed in small populations.
• Stay curious about the natural world and its processes.