Genetic drift

Definition

Genetic drift is the change in the frequency of alleles in a population due to random sampling of organisms, which can lead to significant differences in genetic makeup over time. It is particularly impactful in small populations where chance events can have a greater effect on allele frequencies, leading to loss of genetic variation and potentially influencing the evolutionary trajectory of the population.

5 Must Know Facts For Your Next Test

1. Genetic drift can lead to the fixation or loss of alleles within small populations, resulting in decreased genetic diversity.
2. Unlike natural selection, which involves differential survival based on advantageous traits, genetic drift is random and does not favor any specific traits.
3. The impact of genetic drift is more pronounced in isolated populations, such as those found in metapopulations, where migration may be limited.
4. Genetic drift can influence evolutionary processes by allowing populations to diverge genetically over time, potentially leading to speciation.
5. The effects of genetic drift are more significant in smaller populations because random events can drastically alter allele frequencies compared to larger populations where such changes are buffered.

Review Questions

• How does genetic drift differ from natural selection in terms of its impact on a population's genetic composition?
  • Genetic drift differs from natural selection in that it is a random process rather than a selective one. While natural selection promotes traits that enhance survival and reproduction, genetic drift leads to changes in allele frequencies due to random sampling events. This means that under genetic drift, alleles can become more or less common without regard to their effect on fitness, which can result in the loss of beneficial alleles or the fixation of harmful ones.
• Discuss the implications of genetic drift on the conservation of endangered species within metapopulation dynamics.
  • In metapopulation dynamics, genetic drift can have serious implications for the conservation of endangered species. When populations are fragmented and small, genetic drift can lead to reduced genetic diversity and increased homozygosity. This makes populations more susceptible to diseases and reduces their ability to adapt to environmental changes. Conservation efforts must consider the effects of genetic drift by promoting connectivity between populations to maintain gene flow and mitigate the negative consequences of isolation.
• Evaluate the role of genetic drift in shaping the evolutionary paths of isolated populations and how this might lead to speciation.
  • Genetic drift plays a critical role in shaping the evolutionary paths of isolated populations by driving divergence through random changes in allele frequencies. In small, isolated populations, these random fluctuations can lead to significant differences over generations, potentially resulting in reproductive isolation. As these populations evolve independently due to genetic drift, they may develop distinct characteristics that eventually contribute to speciation, as they become less able to interbreed with their ancestral population due to accumulated genetic differences.

Related terms

Founder Effect: A phenomenon that occurs when a new population is established by a small number of individuals, leading to reduced genetic diversity and a different allele frequency than the source population.

Bottleneck Effect: A sharp reduction in population size due to environmental events or human activities, resulting in a loss of genetic variation and changes in allele frequencies.

Allele Frequency: The proportion of a specific allele among all alleles for a particular gene in a population, which can be influenced by factors such as natural selection, genetic drift, and mutation.