1. Earlobe attachment is a trait that operates based on Mendelian genetics
Free earlobes are dominant (E)
Attached earlobes are recessive (e)
Two individuals mate, what is the probability that the offspring will have attached earlobes? Use a Punnett square to help you answer this question (1pt)
Parent 1 Genotype: Heterozygous for free earlobes (Ee)
Parent 2 Genotype: Homozygous recessive for attached earlobes (ee)
2. Explain the difference between: (1 pt; 0.5 pts each)
a. Dominant and Recessive
b. Phenotype and Genotype
3. What is phenotypic plasticity, and in what ways can it be adaptive (1pt)
4. Why is the Hardy-Weinberg equilibrium used in population genetics, and what can it tell us about the forces acting on a population? (1pt)
5. In human populations in Africa, two common alleles affect the structure of hemoglobin, the protein that carries oxygen on red blood cells. What is regarded as the normal allele (the allele common in European populations) is usually labeled A, and the sickle-cell allele is designated S. There are three hemoglobin genotypes, and the phenotypes associated with these genotypes can be distinguished in a variety of ways. In one African population of 10,000 adults, for example, there are 3,000 AS individuals, 7,000 AA individuals, and 0 SS individuals. (3pts, 1pt each)
a. Suppose that these individuals were to mate at random. What would be the frequency of the A and S alleles among the gametes that they produced?
b. What would be the frequency of the three genotypes that resulted from random mating?
c. Is the original population of adults in Hardy–Weinberg equilibrium?
6. The three common genotypes at the hemoglobin locus have very different phenotypes: SS individuals suffer from severe anemia, AS individuals have a relatively mild form of anemia but are resistant to malaria, and AA individuals have no anemia but are susceptible to malaria. The frequency of the S allele among the gametes produced by the first generation of a central African population is 0.2. (3pts, 1pt each)
a. Assuming that mating occurs at random, what are the frequencies of the three genotypes among zygotes produced by this population?
b. In this area, no SS individuals survive to adulthood, 70% of the AA individuals survive, and all of the AS individuals survive. What is the frequency of each of the three genotypes among the second generation of adults?
c. What is the frequency of the S allele among gametes produced by these adults?
