Genetic drift

Definition

Genetic drift is a mechanism of evolution that involves random changes in the frequency of alleles (gene variants) in a population over time, primarily due to chance events. This process can lead to significant changes in small populations, impacting their genetic diversity and potentially leading to the fixation or loss of certain alleles, which influences evolutionary dynamics and speciation.

5 Must Know Facts For Your Next Test

1. Genetic drift has a more pronounced effect in smaller populations where chance events can lead to larger fluctuations in allele frequencies.
2. It can result in the random loss of alleles, reducing genetic variation and potentially making populations more vulnerable to environmental changes.
3. Unlike natural selection, which involves differential survival based on advantageous traits, genetic drift is purely random and does not favor any specific allele.
4. Genetic drift can lead to speciation by causing populations to diverge genetically when they become isolated and experience different random events over time.
5. Recurrent genetic drift can influence evolutionary trajectories, making it an essential factor in understanding how species evolve and adapt.

Review Questions

• How does genetic drift differ from natural selection in terms of its effects on allele frequencies within a population?
  • Genetic drift is a random process that causes changes in allele frequencies due to chance events, while natural selection involves the differential survival and reproduction of individuals based on advantageous traits. In small populations, genetic drift can lead to significant changes in allele frequencies even without any selective pressure, whereas natural selection consistently favors alleles that provide benefits in the environment. This means that while both processes influence evolution, genetic drift operates independently of an allele's adaptive value.
• Discuss the implications of the founder effect on the genetic diversity of newly established populations.
  • The founder effect occurs when a small group establishes a new population, leading to reduced genetic diversity compared to the original population. Because this new population is formed from only a few individuals, certain alleles may be overrepresented or completely absent. This lack of genetic variation can hinder the population's ability to adapt to environmental changes and increase the risk of extinction. The founder effect highlights how random sampling can significantly impact the evolutionary trajectory of isolated populations.
• Evaluate the role of genetic drift in the process of speciation and how it contributes to the divergence of populations over time.
  • Genetic drift plays a crucial role in speciation by causing random changes in allele frequencies that may lead to reproductive isolation between populations. When two populations become separated geographically or ecologically, they may experience different random events that influence their genetic makeup independently. Over time, this can result in significant genetic divergence and eventually lead to the formation of new species. By reducing gene flow and amplifying random differences, genetic drift thus contributes to the complexity and richness of biodiversity we observe today.

Related terms

Bottleneck Effect: A significant reduction in population size due to environmental events or human activities that reduces genetic diversity and can lead to genetic drift.

Founder Effect: A phenomenon that occurs when a small group from a larger population establishes a new population, resulting in reduced genetic variation and altered allele frequencies.

Allele Frequency: The relative frequency of an allele at a genetic locus in a population, which can be affected by processes such as genetic drift, natural selection, and gene flow.