Allele frequency

Definition

Allele frequency refers to how often a particular allele appears in a population compared to other alleles for the same gene. This measure is crucial in understanding genetic variation within a population, as it influences traits and adaptations over generations. Allele frequencies can change over time due to factors such as natural selection, genetic drift, and gene flow.

5 Must Know Facts For Your Next Test

1. Allele frequencies are typically expressed as a proportion or percentage of the total number of alleles for a particular gene in the population.
2. The Hardy-Weinberg principle provides a mathematical framework to predict allele frequencies under specific conditions of genetic equilibrium.
3. Changes in allele frequency can indicate evolutionary processes occurring within a population over time.
4. A dominant allele does not always have a higher frequency than a recessive allele; it depends on the specific population dynamics.
5. Monitoring allele frequencies is essential for conservation biology, as it helps assess genetic diversity and the health of endangered populations.

Review Questions

• How do natural selection and genetic drift influence allele frequencies in a population?
  • Natural selection affects allele frequencies by favoring alleles that confer advantages in survival and reproduction, thus increasing their prevalence over time. In contrast, genetic drift causes random changes in allele frequencies due to chance events, particularly in smaller populations where certain alleles may become more common or lost entirely. Both processes contribute to the dynamic nature of allele frequencies and can lead to significant evolutionary changes.
• Explain how the Hardy-Weinberg principle can be used to predict allele frequencies in a non-evolving population.
  • The Hardy-Weinberg principle states that in a non-evolving population, allele frequencies will remain constant from generation to generation under certain conditions: no mutation, random mating, no natural selection, extremely large population size, and no gene flow. By applying this principle, researchers can calculate expected genotype frequencies based on observed allele frequencies, allowing them to assess whether real populations are evolving or remaining stable over time.
• Evaluate the impact of gene flow on allele frequencies and its significance for population genetics.
  • Gene flow can significantly impact allele frequencies by introducing new alleles into a population or changing the proportions of existing alleles. This exchange of genetic material between populations can increase genetic diversity and enhance adaptability to environmental changes. Understanding gene flow is vital in population genetics because it helps explain how populations maintain connectivity and how they respond to selective pressures, ultimately influencing evolutionary trajectories.

Related terms

Genetic Drift: A random process that can cause allele frequencies to change over time, particularly in small populations, due to chance events.

Natural Selection: The process through which traits that enhance survival and reproduction become more common in a population, affecting allele frequencies.

Gene Flow: The transfer of genetic material between populations, which can introduce new alleles and alter allele frequencies.