EXTENSIONS OF HARDY-WEINBERG PRINCIPLE

Answer Key

Calculate the answers of the following questions. Use the Hardy-Weinberg Principle to complete the assignment. Show your work.

1. In a large, random-mating population with no forces acting to change gene frequencies, the frequency of homozygous recessive individuals for the characteristic of extra-long eyelashes is 90 per 1000 individuals.

What is the frequency of the recessive allele? 0.09

What is the frequency of the dominant allele? 0.91

What is the frequency of the heterozygous individual? 2 x 0.09 x 0.91 = 0.16

2. Allele A is present in a large random mating population at a frequency of 54 per 100 individuals.

What is the frequency of allele a? 0.46

What is the proportion of individuals in the population expected to be homozygous for A? 0.29

What is the proportion of individuals in the population expected to be homozygous for a? 0.21

What is the proportion of individuals in the population expected to be heterozygous? 0.50

3. The North American human population is similar to the ideal Hardy-Weinberg population in that it is very large and generally random-mating. (Mutation and migration are relatively minor forces.) The scientist, Randy M. Mateng, analyzed a group of individuals for a blood type called the MN blood typing. His results are as follows:

MM MN NN

Observed individuals 3210 4670 2120

What is the frequency of the M allele? 0.57

What is the frequency of the N allele? 0.43

What would the frequencies be 10 generations from now? M = 0.57

N = 0.43

4. Cystic fibrosis is a recessive disease that primarily affects Caucasian individuals. In the American population the frequency of the allele for cystic fibrosis is 22 per 1000 individuals.

What is the frequency of the cystic fibrosis allele? 0.022

What is the frequency of the normal or dominant allele? 0.978

What percentage of the population will have cystic fibrosis? 0.05%

What percentage of the population will be a carrier (heterozygous)? 4.3%

5. Phenylketonuria (PKU), a genetic disorder due to homozygosity for a certain recessive allele, occurs in about 1 person in 15,000.

What is the frequency of the PKU allele? 1/15,000 = 0.008

What is the frequency of the normal allele? 0.992

What is the frequency of the carrier (heterozygous) individual? 0.016 or 1.6%

6. In the United States, about 45% of the white population has blood type O, 41% type A, 10% type B, and 4% type AB. Determine the frequencies of the three alleles of the ABO blood type. (Hint: Type A blood can be either AA or AO; type B blood can be either BB or BO; type AB is AB; type O is OO.)

Frequency of A allele .25

Frequency of B allele .08

Frequency of O allele _ .67

(Based on p + q + r = 1 and (p + q + r)² = 1.

If p = A, q = B, and r = O, then

1. r² = .45 and r = .67

2. pq = .04

3. p² + 2pr = .41 and

4. q² + 2qr = .10

Use the quadratic equation to solve #3 and #4.