Genetic drift

Definition

Genetic drift is a mechanism of evolution that refers to random changes in the frequency of alleles (gene variants) in a population over time. These changes are often more pronounced in small populations where chance events can lead to significant fluctuations in allele frequencies, ultimately affecting the genetic diversity and evolutionary trajectory of that population.

5 Must Know Facts For Your Next Test

1. Genetic drift can lead to the fixation or loss of alleles, meaning that certain alleles may become the only variant present or disappear completely from a population.
2. This process is more impactful in small populations because random events can significantly alter allele frequencies, whereas large populations tend to buffer against such changes.
3. Unlike natural selection, which favors advantageous traits, genetic drift is completely random and does not necessarily promote adaptation.
4. Genetic drift can contribute to speciation by causing populations to diverge genetically over time, especially if they become isolated from one another.
5. The effects of genetic drift are often studied through models that simulate allele frequency changes over generations, demonstrating its influence on evolutionary outcomes.

Review Questions

• How does genetic drift differ from natural selection in terms of its impact on allele frequencies?
  • Genetic drift differs from natural selection primarily in that it is a random process, while natural selection involves differential survival and reproduction based on advantageous traits. In genetic drift, allele frequencies can fluctuate purely by chance, leading to random fixation or loss of alleles regardless of their adaptive value. This randomness means that genetic drift can have significant effects on small populations, while natural selection consistently drives populations toward traits that improve fitness.
• What are the consequences of the bottleneck effect on genetic diversity and how does it relate to genetic drift?
  • The bottleneck effect results from a sharp reduction in population size due to environmental events or other factors, leading to a loss of genetic diversity. This reduction can cause certain alleles to be lost entirely or fixed at higher frequencies purely by chance, which exemplifies genetic drift. The consequence is that the remaining population may exhibit limited genetic variability, making it less adaptable to environmental changes and increasing the risk of extinction.
• Evaluate how both genetic drift and the founder effect can lead to differences in allele frequencies between populations and the implications for biodiversity.
  • Both genetic drift and the founder effect can significantly lead to variations in allele frequencies between populations by emphasizing the role of random chance in evolution. Genetic drift can cause allele frequencies to change unpredictably over generations in small populations, while the founder effect occurs when a small group establishes a new population with limited gene variation from the original. Together, these processes can result in distinct evolutionary paths for different populations, ultimately impacting biodiversity by creating unique genetic profiles that may affect their ability to survive environmental changes.

Related terms

natural selection: A process where organisms better adapted to their environment tend to survive and produce more offspring, influencing allele frequencies in a population.

bottleneck effect: A significant reduction in population size due to environmental events or human activities, which can lead to reduced genetic diversity and altered allele frequencies.

founder effect: A phenomenon that occurs when a small group of individuals establishes a new population, leading to a limited gene pool and different allele frequencies compared to the original population.