Problem
I. Describe what we mean by a "genetic mutation"?
II. What are the THREE possible impacts of a genetic mutation on the reproductive fitness of an individual? In other words, how could a genetic mutation affect the survival and reproduction of an individual?
III. Where should a mutation occur in order to be a force of evolution? In other words, which cells must carry the mutation in order for it to impact the next generation?
IV. In humans, "free" or detached earlobes are a dominant characteristic and attached earlobes are recessive. In data collected in the early 1970's, the following percentage of people from two Indian ethnic groups had detached (vs. attached) earlobes: Suri- 79% vs. Ahom- 38%. Prior to the mid 20th century, these two groups had not regularly interacted, but in recent years, they have established mutually beneficial trade relations. As a result of this newfound economic partnership, social exchanges in the form of marriage partners have now begun to take place. Before intermarriage, the two Indian populations were very different with respect to their frequencies of detached earlobes. After several generations of exchanging marriage partners, do you think these two groups would have become more or less similar with regard to their frequencies of detached earlobes?
V. In the Indian example described in the previous question, what do you think will happen to other phenotypic traits (besides earlobe attachment)? Will these become more or less similar between the two populations?
VI. Height in humans is a polygenic trait exhibiting continuous variation. Consider height in these two Indian populations: the Ahom are much shorter on average than the Suri. After several generations of intermarriage, what phenotypes would you expect to see among the admixed descendants?
VII. Genetic drift refers to random influences on gene frequencies. These random events result in the "drifting" up or down of allele frequencies from one generation to the next. In what size of population does genetic drift have the most effect?
VIII. What is an example of a bottleneck event that might reduce the population size of a group of animals? In your answer be sure to specify which animal species might experience this. Give a little description of the "event".
IX. What happens to the genetic variation of a population when you drastically reduce the number of individuals in that population?
X. On what does natural selection act? (Think individuals versus populations and genotypes versus phenotypes.)
XI. Some recessive genetic diseases are almost always fatal. However, in some populations, the recessive allele that causes the disease is found in greater frequencies than expected because there is a "heterozygous advantage" for those carriers of the recessive allele. We see this with the sickle cell allele. In this scenario, the sickle cell allele is maintained in populations with endemic malaria. What is this type of selection called? In other words, selection that maintains two alleles, rather than favoring one or the other is called what?
XII. In the scenario described in the previous question (sickle cell anemia in areas with high malaria), which genotype has the highest fitness?