Hardy Weinberg Practice Problems
Instead of a lab this week, you are going to complete 5 practice problems where you will apply the Hardy Weinberg Principal. You can show as much or as little of your work as you want, but you can only receive partial credit if I can see how you calculated your answer! NOTE: Assume that all populations in the following questions are in Hardy-Weinberg equilibrium!
Basic Background:
The Hardy Weinberg Principal allows you to predict genotypic and allelic frequencies in a stable population for a gene that has two alleles (i.e. A and a). Here are the equations you need:
p + q = 1
p2 + 2pq + q2 = 1
· The frequency of the dominant allele is represented by p.
· The frequency of the recessive allele is represented by q.
· The frequency of the genotype AA is represented by p2.
· The frequency of the genotype Aa is represented by 2pq.
· The frequency of the genotype aa is represented by q2.
The problems:
1. The frequency of two alleles in a gene pool is 0.23 (A) and 0.77(a).
a. Calculate the percentage of heterozygous (Aa) individuals in the population.
b. Calculate the percentage of homozygous recessive (aa) individuals in the population.
2. In a certain species of goat, there is a dominant allele for brown coat color (B) and a recessive allele for white coat color (b). The frequency of white goats, which is the recessive homozygote genotype (bb), is 0.16. Calculate the percentage of individuals homozygous for the dominant allele (BB).
3. Allele T, for the ability to taste a particular chemical, is dominant over allele t, for the inability to taste the chemical. One hundred university students were surveyed and 8 were found to be nontasters (tt).
a. Calculate the percentage of heterozygous (Tt) students.
b. What are the frequencies of the two alleles? (T and t)
4. In corn, kernel color is governed by a dominant allele for white color (W) and by a recessive allele for yellow color (w). A random sample of 100 kernels from a population that is in H-W equilibrium reveals that 4 kernels are yellow (ww) and 96 kernels are white.
a. Calculate the frequencies of the yellow and white alleles in this population.
b. Calculate the percentage of this population that is heterozygous.
5. Sickle-cell anemia is an interesting genetic disease. Normal homozygous individuals (SS) have normal blood cells that are easily infected with the malarial parasite. Thus, many of these individuals become very ill from the parasite and many die. Individuals homozygous for the sickle-cell trait (ss) have red blood cells that readily collapse when deoxygenated. Although malaria cannot grow in these red blood cells, individuals often die because of the genetic defect. However, individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause mortality. In addition, malaria cannot survive well within these “partially defective” red blood cells. Thus, heterozygotes tend to survive better than either of the homozygous conditions. If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene?
