1. Let’s say you have a trait (a phenotype) that is controlled by 1 gene (coat color) and 2 alleles (blue coat allele and red coat allele). The alleles are codominant, so a heterozygote is green. In a population of animals you see 100 red coat individuals, 100 blue coat individuals, and 50 green coat individuals.

a. What are the phenotype frequencies in this population?

b. What are the observed genotype frequencies in this population?

c. What are the allele frequencies in a gene pool for this population?

d. What genotype frequencies would you expect if this population were not evolving?

2. Several genes control wing shape in Drosophila melanogaster. One of wing shape phenotypes is normal / curly winged phenotype. This is a 1 gene / 2 allele gene system in which the normal wing allele is dominant over the curly wing allele. You have found a population of D. melanogaster living in the sub-basement of Combs Hall on campus. Combs Hall was the sciences building until 1998. You have found that 5% of the population has curly wings and 95% of the population has normal size wings.

a. What are the types of phenotypes in this population.

b. What are the possible genotypes of the 2 phenotypes.

c. What are the phenotype frequencies?

d. What are the observed genotype frequencies?

e. If you assume this population is a large, random mating population that is not undergoing evolution, what are the genotype frequencies? First, figure the allele frequencies in the gene pool.

3. You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following:

a. The frequency of the “aa” genotype.

b. The frequency of the “a” allele.

c. The frequency of the “A” allele.

d. The frequencies of the genotypes “AA” and “Aa.”

e. The frequencies of the two possible phenotypes if “A” is completely dominant over “a.”

4. Sickle-cell anemia is a globally important disease and it has interesting genetics. Normal homozygous individials (SS) have normal red blood cells AND these normal red blood cells 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 (i.e. sickle-cells). Although malaria cannot grow in these red blood cells, individuals often die because of the misshapen cells. However, individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause mortality. In addition, malarial parasites 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? Assume the population starts in Hardy-Weinberg equilibrium.

a. What are the phenotype frequencies in this population?

b. What are the observed genotype frequencies in this population?

c. What are the allele frequencies in a gene pool for this population?

d. Would you expect this population to remain in Hardy-Weinberg equilibrium (not evolve)? (Be sure to say No!) Why do you say that?