Genetic drift

Definition

Genetic drift is the random change in allele frequencies in a population from one generation to the next due to chance events. This process can lead to significant changes in a population's genetic makeup over time, especially in small populations where random events can have a larger impact. It plays an important role in evolution alongside natural selection, influencing genetic variation and the overall dynamics of populations.

5 Must Know Facts For Your Next Test

1. Genetic drift can result in the fixation or loss of alleles in small populations, leading to reduced genetic diversity over generations.
2. Unlike natural selection, genetic drift is not driven by the fitness advantages of certain traits; it is purely stochastic.
3. Genetic drift can have substantial effects on populations that are isolated or have limited gene flow with other populations.
4. In larger populations, genetic drift has less impact because random changes are diluted by the larger pool of alleles.
5. Genetic drift can lead to speciation if populations diverge significantly due to random changes over time.

Review Questions

• How does genetic drift differ from natural selection in terms of its effects on populations?
  • Genetic drift differs from natural selection as it is a random process that leads to changes in allele frequencies without regard to the adaptive value of traits. While natural selection favors individuals with advantageous traits, increasing their reproductive success and passing those traits to future generations, genetic drift can result in random increases or decreases in allele frequencies that do not necessarily benefit or harm the population. This randomness can lead to significant evolutionary changes, especially in small populations.
• Discuss the implications of the bottleneck effect and founder effect on genetic drift and population genetics.
  • The bottleneck effect occurs when a population's size is drastically reduced due to environmental events, causing a significant loss of genetic diversity and skewed allele frequencies. This can result in increased homozygosity and reduced adaptability. The founder effect happens when a new population is established by a small group, leading to limited genetic variation compared to the original population. Both effects illustrate how genetic drift can alter the genetic structure of populations and affect their long-term evolutionary trajectories.
• Evaluate how genetic drift interacts with other evolutionary processes like gene flow and mutation in shaping biodiversity.
  • Genetic drift interacts with gene flow and mutation in complex ways that shape biodiversity. Gene flow introduces new alleles into a population, which can counteract the effects of genetic drift by increasing genetic diversity and reducing the impact of random allele changes. Mutation adds new genetic variations that can become subject to both genetic drift and natural selection. Together, these processes create dynamic evolutionary landscapes where small, isolated populations may experience significant shifts due to drift, while larger populations maintain more stability through gene flow and selection.

Related terms

Bottleneck effect: A sharp reduction in the size of a population due to environmental events or human activities, leading to a loss of genetic diversity.

Founder effect: A type of genetic drift that occurs when a small group of individuals establishes a new population, carrying only a fraction of the original population's genetic variation.

Allele frequency: The relative frequency of an allele (variant of a gene) at a genetic locus in a population, expressed as a proportion or percentage.