10.1.3 The Hardy-Weinberg Equation

Question 1

Hardy-Weinberg equation

Answer 1

• Review: According to the Hardy-Weinberg theory, for nonevolving populations, sexual recombination alone will not alter the relative frequencies of alleles
• The Hardy-Weinberg equation is derived from the Hardy-Weinberg theory. The equation is used to predict allelic and genotypic frequencies in a nonevolving population. For a specific pair of alleles, the Hardy-Weinberg equation accounts for all of the genotypic frequencies of a population.
- The Hardy-Weinberg equation is p^2+ 2pq + q^2 = 1.
- The Hardy-Weinberg equation is often used in the study of populations. The equation can be used to calculate the frequencies of alleles in a gene pool if the frequencies of genotypes are known and vice versa.
- Review: The genotype is the allelic composition for a
particular trait. Alleles are different forms of a given gene.
- To the left are the initial components of the Hardy-Weinberg equation. In a given population, all of the alleles of a particular gene are represented in the equation. For a gene with two alleles, p equals the frequency of the dominant allele, and q is the frequency of the recessive allele. The total frequency = 1.
- The expression p^2+ 2pq + q^2 defines the complete
Hardy-Weinberg equation. - For the alleles A and a, the four possible genotypes are: AA, Aa, aA, and aa. The frequency of the dominant A allele = p. The frequency of the homozygous dominant AA genotype is (p)(p), or p
2. The expression 2pq is the frequency of the heterozygous genotype Aa. The expression q 2
represents the frequency of the homozygous recessive aa genotype.
- If the frequency of either allele is known, you can determine the frequency of the genotypes and vice versa.

Question 2

Which of the following pieces of information would allow you to calculate the frequency of the homozygous dominant genotype for a given trait in a population?

Answer 2

• the frequency of the recessive allele

Question 3

Which of the following is equal to the equation for the frequency of genotypes (p2 + 2pq + q2 = 1)?

Answer 3

• (p + q)^2

Question 4

A randomly mating population has an established frequency of 25% (0.25) for organisms homozygous recessive for a given trait. The frequency of this recessive allele in the gene pool is

Answer 4

• 0.5

Question 5

For a gene with two alleles in a given population, the total frequency (p + q) is:

Answer 5

• 1

Question 6

What is the highest possible frequency of heterozygotes in a population for a gene with two alleles if the population is in Hardy–Weinberg equilibrium?

Answer 6

• 0.5

Question 7

In a randomly mating population of animals called fuzzles the frequency of the dominant phenotype of pink fur is 64%. The recessive phenotype is white fur. The frequency of the pink fur allele is

Answer 7

• 0.4