HARDY WEINBERG EQUILIBRIUM HOMEWORK

Show all of your work for each problem.

• Deals w/ distribution of genes within a population – says that frequency of an allele in a gene pool will remain constant unless acted upon by other agents
• Hardy Weinberg applies to only stable populations, and there are 5 conditions that must be met in order for H-W equilibrium to be maintained:

• Large population size
• No migration in or out
• No mutations
• Random mating
• No natural selection

• Now, in nature these conditions are rarely met, so why use H-W? You can use H-W frequencies as a basis for comparison when studying populations in which gene pools are changing. If a population’s frequencies are changing, then you can try to determine which of the above conditions is not being met.

The Equations:

Equation for allele frequency: p + q = 1

p = frequency of ___________________ allele

q = frequency of ___________________ allele

Equation for genotype frequency: p² + 2pq + q² = 1

p² = frequency of _________________________ genotype

2pq = frequency of _________________________ genotype

q²= frequency of __________________________ genotype

Practice Problems:

• Calculate allele frequency and genotype frequency for a herd of horses in which p = 0.32

• A flock of 435 Ibis (a bird) includes 337 individuals with pink legs and 98 individuals with white legs. Pink legs are dominant to white legs.

What is the frequency of the q allele (white legs)?

What is the frequency of the p allele (pink legs)?

What is the frequency of heterozygotes in this population?

What is the frequency of birds that are homozygous dominant for pink legs?

• If 78 out of 240 individuals in a population have blue eyes, a recessive trait, what percentage of the population are heterozygotes? Homozygous dominant? Assuming Hardy-Weinberg Equilibrium, how many individuals in a population of 5,000 would be homozygous dominant?

• In rabbits, white coat is recessive to brown coat color. In a population of rabbits in England, the frequency of the homozygous dominant genotype is 0.42

What is the frequency of the p allele?

What is the frequency of the q allele?

What is the frequency of the homozygous recessive genotype?

What is the frequency of the heterozygous genotype?

• Sickle-cell anemia is a genetic disease in which both homozygous conditions are selected against, and heterozygotes have a genetic advantage. Individuals who are homozygous dominant have normal red blood cells which are easily infected with malaria and subsequently are prone to death. Individuals who are homozygous recessive have red blood cells that cannot be infected by the malaria parasite; however, their red blood cells sickle easily when they become deoxygenated. Many individuals die from this condition. Individuals who are heterozygous have some red blood cells that sickly, however, the majority do not. In addition, these individuals are resistant to malaria. In a small village in Africa, 15% of the population is born with the homozygous recessive condition.

What is the allele frequency for the dominant allele?

What is the allele frequency of the recessive allele?

What are the three genotype frequencies?

Assuming Hardy-Weinberg Equilibrium, how many individuals in a neighboring village of 3500 would be expected to be heterozygous?