Hardy Weinberg

Population Genetics & Evolution
Hardy-Weinberg Information

Summary Outline of Hardy-Weinberg:

     A. Population Genetics Terminology
           1. Population
           2. Gene Pool
           3. Evolution

     B. Hardy-Weinberg
           1. H-W Principle
           2. H-W Equilibrium
           3. H-W Calculations
           4. H-W Example Problem

See Below For More Information

     A. Population Genetics Terminology
           1. Population - All the members of a species that occupy a particular area at the same time

           2. Gene Pool - All of the genes found in members of a population

           3. Evolution - A change in the frequency of genes in a population's gene pool from one generation to the next

     B. Hardy-Weinberg
           1. H-W Principle - A theoretical model for a population that does not change genetically from one generation to the next

           2. H-W Equilibrium - A mathematical and theoretical condition in which no evolution occurs. All five conditions below must be met for H-W equilibrium to exist.
                a. No mutations.
                b. No selection pressure (no genotype has a reproductive advantage over another).
                c. No mating preferences (mating is totally random with respect to genotype).
                d. Population is isolated (no exchange of genes through gene flow, immigration or emigration).
                e. Population is large in size (eliminates situation of genetic drift or the founder effect).

           3. H-W Calculations
                a. Variables:
                      1) p - frequency of the dominant allele in the population
                      2) q - frequency of the recessive allele in the population

                b. Equations:
                     1) Allelic Frequencies - (p + q = 1)
                     2) Genotypic Frequencies - (p² + 2pq + q² = 1)
                           a) Homozygous Dominant Genotype = pp = p²b) Heterozygous Genotype = pq = 2pq
                           c) Homozygous Recessive Genotype = qq = q²

           4. H-W Example Problem - If there are 64 brown mice and 36 white mice, what is the frequency of the dominant allele? What is the frequency of the heterozygous condition?
                a. Brown = 64 = 64% = Dominant
                b. White = 36 = 36% = Recessive
                c. q² = 0.36
                    q = 0.6
                d. p + q = 1
                     p = 0.4
                e. Heterozygous = 2pq
                    2 * 0.4 * 0.6 = 0.48
                f. Check your work
                    p² + 2pq + q² = 1
                    0.16 + 0.48 + 0.36 ? = ? 1
                    1.00 = 1.00 Correct Answer!!

To test your knowledge about Hardy-Weinberg Information, click on the H-W Questions Link at the top of this page. After you answer the questions, be sure to check your responses by clicking on the H-W Answers Link.