Allele frequency

Definition

Allele frequency refers to how often a particular allele appears in a population relative to the total number of alleles for that gene. It’s a key concept in understanding genetic variation and evolution, influencing how traits are inherited and how populations adapt over time. Changes in allele frequency can indicate evolutionary processes such as natural selection, genetic drift, and gene flow.

5 Must Know Facts For Your Next Test

1. Allele frequencies can be influenced by various factors including mutation rates, selection pressure, migration, and genetic drift.
2. In a population at Hardy-Weinberg equilibrium, allele frequencies remain constant from generation to generation unless disturbed by outside forces.
3. Calculating allele frequency helps in understanding the genetic diversity of populations and can be essential for conservation efforts.
4. Allele frequencies are usually expressed as a fraction or percentage of the total alleles present for that gene in the population.
5. Small populations are more susceptible to changes in allele frequencies due to genetic drift, which can lead to rapid shifts in genetic traits.

Review Questions

• How do changes in allele frequency relate to evolutionary processes such as natural selection?
  • Changes in allele frequency are fundamental to the process of evolution. Natural selection acts on individuals with certain traits, leading to increased survival and reproduction of those with advantageous alleles. Over generations, this can cause those advantageous alleles to become more common, shifting allele frequencies within the population. Thus, tracking these changes helps us understand how populations evolve over time.
• Discuss the role of mutation and gene flow in altering allele frequencies within a population.
  • Mutation introduces new alleles into a population's gene pool, potentially altering allele frequencies if these new alleles confer an advantage or disadvantage. Gene flow, or the movement of alleles between populations through migration, can also change allele frequencies by introducing new genetic variations or homogenizing differences between populations. Both processes contribute to the dynamic nature of genetic variation and evolution.
• Evaluate how Hardy-Weinberg equilibrium provides a baseline for understanding shifts in allele frequency due to environmental pressures.
  • Hardy-Weinberg equilibrium serves as a model for predicting allele frequencies under ideal conditions where no evolutionary forces are acting. When environmental pressures such as climate change or habitat destruction occur, they disrupt this equilibrium. By comparing observed allele frequencies against Hardy-Weinberg expectations, researchers can identify how much change has occurred due to selection pressures or other evolutionary mechanisms, making it a powerful tool for studying population genetics.

Related terms

Genotype Frequency: The proportion of different genotypes in a population, which is determined by the combination of alleles an individual possesses.

Hardy-Weinberg Principle: A principle that describes the expected distribution of genotypes in a population under certain conditions, helping to predict allele frequencies when the population is in equilibrium.

Mutation: A change in the DNA sequence that can create new alleles and alter allele frequencies within a population.