10.1.5 Using the Hardy-Weinberg Theory II

Question 1

hardy-weinberg theory ii

Answer 1

• Review: The Hardy-Weinberg theory can be used to predict the frequencies of certain diseases in populations.
• The Hardy-Weinberg equation is P^2+ 2pq + q^2= 1. In this equation, the variable p represents the frequency of the dominant allele and q represents the frequency of the recessive allele.
• Given the incidence of a disease in a population, the Hardy-Weinberg theory can predict the complete genotypic and allelic frequencies for that trait.
- Use the Hardy-Weinberg theory to determine the probability that two carriers of sickle cell anemia will meet and produce offspring.
- In a sample of 400,000 African-Americans, 1,000 individuals are afflicted with sickle cell anemia. The disease is expressed in homozygous recessive (aa) individuals.
- Because the disease results from the homozygous recessive condition, the value q^2 represents the frequency of individuals with sickle-cell anemia. Solve for q^2 and then determine the values of q and p.
q^2 = 1,000/400,000
q^2 = 0.0025
q = 0.05
- Once the value of q is determined, the value of p can be determined.
p + q = 1
p + 0.05 = 1
p = 0.95

Question 2

One out of 10,000 babies in the US is born with phenylketonuria (PKU) a recessive metabolic disorder that can result in mental retardation. What is the frequency of the PKU allele?

Answer 2

• 0.01

Question 3

If one out of 10,000 babies in the US is born with PKU, a recessive disease, what is the frequency of carriers of the PKU allele?

Answer 3

• 0.0198

Question 4

Taenia pisiformis, a species of tapeworm, is a parasite of domestic dogs and cats. A veterinary clinic is interested in determining whether or not drug resistance (caused by a recessive allele) is evolving in the population, and the following data are obtained:
Year Not
resistant Resistant Total
1999 768 32 800
2000 840 160 1000
Given the data shown, what conclusions can you make about the tapeworm population?

Answer 4

• The tapeworm population is evolving drug resistance.

- In the sample collected in 2000, 480 tapeworms are heterozygous

Question 5

The Hardy–Weinberg equation can be used to

Answer 5

• determine the allele frequencies of a population.

Question 6

In a population of 860 cats there are two alleles at the agouti locus: A-agouti, which controls the presence of yellow bands on individual hairs giving a fine “speckled” appearance, and a-non-agouti, giving a solid color to the hair. The allele frequency of A is 0.9. What would be the number of heterozygotes in the population if it is in Hardy–Weinberg equilibrium?

Answer 6

• 154.8

Question 7

The Hardy–Weinberg principle supports which of the following statements?

Answer 7

• Sexual reproduction alone does not change the frequency of alleles within a population.