Lesson 3: Hardy-Weinberg Equations

Population not evolving, freq of alleles stays constant over generations

Hardy-Weinberg Principle

a fundamental concept in population genetics, stating that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of evolutionary influences. It serves as a model for understanding how evolutionary forces can disrupt genetic equilibrium.

• a population that is not evolving

5 Conditions of H-W Equilibrium

1. No change in allelic frequency due to mutation

2. Random mating

3. No natural selection (the more fit dies)

4. The population size must be extremely LARGE (no genetic drift)

5. No gene flow (immigration, emigration, transfer of pollen)

Genotype frequency equation

p squared + 2pq + q squared = 1

p squared → homozygous dominant

2pq → Heterozygote

q squared → homozygous recessive

Allele frequency equation

p + q = 1

p → A (dominant allele)

q → a (recessive allele)

Chi-Square Tests

• use calculated expected values from solving for both equations of geno and allele

• frequencies to determine the goodness of fit in genetic data. It compares observed and expected frequencies to assess whether a population is in Hardy-Weinberg equilibrium.

• A statistical method used to evaluate the difference between observed and expected frequencies in genetic studies. If the calculated chi-square value is lower than the critical value, it suggests that the population is in Hardy-Weinberg equilibrium → evolution does not occur within the population.