Examples of Genetic Equilibrium

Genetic equilibrium, also known as Hardy-Weinberg equilibrium, is a theoretical concept in population genetics. It describes a state in which the frequency of alleles and genotypes within a population remains constant from generation to generation. In this article, we will explore examples of genetic equilibrium in various organisms, highlighting the conditions necessary for its maintenance and the factors that can disrupt it.

Example 1: Idealized Population

To understand genetic equilibrium, let’s consider an idealized population of organisms. Imagine a population of flowers in which there are two alleles for a particular gene: A and a. The frequency of the A allele is represented by p, and the frequency of the a allele is represented by q. In genetic equilibrium, the frequencies of these alleles will remain constant over time.

Example 2: No Mutation

One condition necessary for genetic equilibrium is the absence of new mutations. Mutations introduce new alleles into a population, which can disrupt the equilibrium. For example, if a new mutation occurs that creates a third allele, B, the equilibrium will be disturbed, and the frequencies of the A and a alleles will no longer remain constant.

Example 3: No Migration

Another condition for genetic equilibrium is the absence of migration. Migration refers to the movement of individuals between different populations. When individuals migrate, they bring their alleles with them, potentially altering the allele frequencies in both populations. If migration occurs, the equilibrium will be disrupted.

Example 4: Random Mating

Genetic equilibrium assumes random mating within a population. This means that individuals have an equal chance of mating with any other individual in the population. If mating is non-random, such as through assortative mating (preferential mating with individuals of similar phenotype), the equilibrium can be disrupted. For instance, if individuals with the AA genotype preferentially mate with other AA individuals, the frequency of the AA genotype will increase, violating the equilibrium.

Example 5: No Natural Selection

Genetic equilibrium assumes the absence of natural selection. Natural selection is the process by which certain traits are favored or disfavored in a population, leading to changes in allele frequencies. If a particular allele provides a selective advantage, its frequency will increase, while alleles with a selective disadvantage will decrease. Natural selection can disrupt genetic equilibrium by altering the frequencies of alleles and genotypes.

Example 6: Large Population Size

Genetic equilibrium is more likely to be maintained in large populations. In small populations, chance events can have a greater impact on allele frequencies, leading to deviations from equilibrium. For example, genetic drift, which is the random fluctuation of allele frequencies due to chance events, can have a significant effect in small populations and disrupt the equilibrium.


Genetic equilibrium is a theoretical concept that describes a state of constant allele and genotype frequencies within a population. The examples of genetic equilibrium in an idealized population, the absence of mutation and migration, random mating, no natural selection, and large population size demonstrate the conditions necessary for its maintenance. Understanding genetic equilibrium helps us study the dynamics of populations and the forces that shape genetic variation. By recognizing the factors that can disrupt equilibrium, scientists can gain insights into the mechanisms of evolution and the maintenance of genetic diversity.

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