How was module 2?
​Here in module 3, you will be introduced with Hardy-Weinberg Law and learn how to use it to calculate allele frequencies and predict genotype frequencies. At the end of this module, you will be able to determine whether a population is at equilibrium or not.

G. Hardy and W. Weinberg found a mathematical model known as the Hardy-Weinberg Law that can be used to determine whether a population is at equilibrium or not. If it is not, then one of the evolutionary forces (you will learn this in Module 4) may have caused it. Remember that you can always calculate allele frequency from genotype frequency but you cannot calculate genotype from allele frequency at all times. However, you can predict genotype frequency if the population is assumed to be at equilibrium.

​Explore the Hardy-Weinberg Equilibrium equations with this video below. Learn why this equation can be useful, its five assumptions, and how to calculate genotype and allele frequencies with p and q values!

You can also watch this video by the Amoeba Sisters to further deepen your understanding about Hardy-Weinberg Equilibrium.

From the Hardy-Weinberg principle and the known allele frequencies, we can also infer the frequencies of the genotypes. Since each individual carries two alleles per gene (Y or y), we can predict the frequencies of these genotypes with a chi square (in this lesson, however, we will not use chi-square). If two alleles are drawn at random from the gene pool, we can determine the probability of each genotype.
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This video below by Paul Andersen also show you how to solve simple Hardy-Weinberg problems. It starts with a brief description of a gene pool and shows you how the formula is derived. He then shows you how to solve a couple of sample problems.

These images summarizes the Hardy-Weinberg Law and how to apply it.