Genetic Equilibrium

A population is a group of individuals of a species that lives in the same area at the same time

Allele Frequency The proportion of an allele in a population. The sum of allele frequencies is one or 100% p + q = 1

The Hardy-Weinberg Principle The Hardy-Weinberg principle describes a population that is not evolving If a population does not meet the criteria of the Hardy-Weinberg principle, it can be concluded that the population is evolving What factors would have to be ABSENT for a population to not evolve?

Hardy-Weinberg Equilibrium The frequency of alleles and genotypes in a population will remain constant from generation to generation if the population is stable and in genetic equilibrium.alleles What factors influence allele frequency in a population? Or, what factors cause allele frequency to change?

Five conditions required in order for a population to remain at Hardy- Weinberg Equilibrium 1.A large breeding populationA large breeding population 2.Random matingRandom mating 3.No change in allelic frequency due to mutationNo change in allelic frequency due to mutation 4.No immigration or emigration (gene flow)No immigration or emigration 5.No natural selectionNo natural selection

When these conditions exist, the population is “not evolving”. Populations are rarely in “true” Hardy-Weinberg Equilibrium, but in some populations the rate of change is so slow that they “appear” to be at equilibrium; then the population can be analyzed to estimate allele and genotype frequencies.

Estimate the Frequency of Alleles in a Population: Hardy-Weinberg Equation p = the frequency of the dominant allele (represented here by A) q = the frequency of the recessive allele (represented here by a)

For a Population in Genetic Equilibrium p + q = 1.0 (The sum of the frequencies of both alleles is 100%.) (p + q) 2 = 1 So, p 2 + 2pq + q 2 = 1 The three terms of this binomial expansion indicate the frequencies of the three genotypes: p 2 = frequency of AA (homozygous dominant) 2pq = frequency of Aa (heterozygous) q 2 = frequency of aa (homozygous recessive)

The allele for black coat is recessive. We can use the Hardy-Weinberg equation to determine the percent of the pig population that is heterozygous for white coat. Hardy-Weinberg equation