Hardy-Weinberg Principle — Overview & Equation

What Is Hardy-Weinberg Equilibrium?

The Hardy-Weinberg Principle is a way to measure if populations are evolving or not. It is a way to compare allele frequencies in a population over time. There are two equations that can be used if a population is in Hardy-Weinberg equilibrium.

There are also five assumptions about the population: random mating (that is, no sexual selection), large or infinite population (no genetic drift), no mutation, no migration, and no natural selection. These five conditions must be met for a population to be in Hardy-Weinberg equilibrium.

If all of these conditions are met, and the allele frequencies are not changing between generations, then the population is in Hardy-Weinberg equilibrium and is not evolving.

In nature, one or more of these assumptions is always being violated. Real, natural populations are compared against the Hardy-Weinberg model to see if they are evolving.

What Is the Hardy-Weinberg Principle?

This principle (also called the Hardy-Weinberg Law) is used to see if populations are evolving. It uses a set of equations to compare the frequency of alleles in populations over time. If certain assumptions are met and allele frequencies remain constant from generation to generation, then the population is not evolving and is in Hardy-Weinberg equilibrium.

What Are the Conditions for Hardy-Weinberg Equilibrium?

The five conditions for Hardy-Weinberg equilibrium are:

• No natural selection
• No mutation
• No migration
• Large or infinite population (no genetic drift)
• Random mating (absence of sexual selection)

These conditions all help keep the gene pool consistent and stable.

How Do We Calculate Hardy-Weinberg Equilibrium?

There are two important equations in Hardy-Weinberg calculations. When there are two alleles for a trait in a population, we know that: $$p+q=1$$ Here, $p$ is the frequency of the dominant allele and $q$ is the frequency of the recessive allele. Together, the two frequencies must add up to 1 (100 percent of the population).

Each organism has two copies of every gene per trait, so allele frequencies are doubled for genotype frequencies. Because of this, genotype frequencies for a population at Hardy-Weinberg proportions can be calculated by squaring the previous equation: $(p+q=1)^2$ $$p^2+2pq+q^2=1$$

Again, $p$ is the frequency of the dominant allele and $q$ is the frequency of the recessive allele. $p^2$ is the frequency of the homozygous dominant genotype. $q^2$ is the frequency of the homozygous recessive genotype. $2pq$ is the frequency of the heterozygous genotype.

(Video) Solving Hardy-Weinberg Problems

by Bozeman Science

The Hardy-Weinberg equation can be confusing. The video above will walk you through the basics and show you how to solve various problems.