Hardy-Weinberg Equilibrium and Population Genetics

Vocabulary terms and definitions covering the math, assumptions, and equations of the Hardy-Weinberg equilibrium as explained by Dr. Gray.

Hardy-Weinberg equilibrium

A principle stating that a population's allele and genotype frequencies are constant unless there is some type of evolutionary force acting upon them.

Population

A group of organisms that are all the same species and can breed with each other and have fertile offspring.

No selection

The first assumption of Hardy-Weinberg equilibrium which states that no natural selection is acting upon the traits, meaning no phenotype has an impact on reproductive fitness.

No mutation

The second assumption of Hardy-Weinberg equilibrium where offspring inherit genes from their parents without any genetic changes.

No migration

The third assumption of Hardy-Weinberg equilibrium stating that individuals cannot move into or out of the population.

Large population

The fourth assumption of Hardy-Weinberg equilibrium; this is necessary because small populations are more vulnerable to genetic drift.

Random mating

The fifth assumption of Hardy-Weinberg equilibrium where organisms mate without any specific choice.

Baseline comparison

The reason Hardy-Weinberg equilibrium is useful despite being unrealistic in nature, as it provides a constant to compare against an evolving population.

$$p$$

The frequency of the dominant allele in the population.

$$q$$

The frequency of the recessive allele in the population.

$$p + q = 1$$

The Hardy-Weinberg equation used specifically for calculating allele frequencies.

$$p^2 + 2pq + q^2 = 1$$

The Hardy-Weinberg equation used for calculating genotype frequencies.

$$p^2$$

The frequency of the homozygous dominant genotype ($GG$).

$$2pq$$

The frequency of the heterozygous genotype ($Gg$).

$$q^2$$

The frequency of the homozygous recessive genotype ($gg$).

Genotype frequency vs. Allele frequency

Genotype frequency refers to the frequency of pairs like $GG$, $Gg$, or $gg$, while allele frequency refers to the frequency of individual alleles like $G$ or $g$.