1.
What two key questions do the authors suggest evolutionary biologists ask? Explain how the analysis of HIV/AIDS presented in this chapter illustrates the scope of evolutionary biology. List as many evolutionary questions as you can identify from Chapter 1.
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
2.
Compare and contrast the HIV/AIDS epidemics in sub-Saharan Africa, South America, Asia, and Western Europe and North America. What is the prevalence of HIV/AIDS in each region? Where is it growing fastest? Which sectors of the population are most at risk? What is the primary mode of transmission?
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
3.
Describe the basic structure and function of HIV, with special attention to the roles of surface proteins and reverse transcriptase in its life cycle. Why, in general, are viral diseases so hard to treat?
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
4.
How does HIV cause AIDS? What is the actual cause of death for AIDS patients?
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
5.
List and briefly describe the steps leading to AZT resistance, including experimental evidence for each as appropriate. Be sure to clearly explain the features of HIV that most directly lead to this problem. Then relate this process to the multidrug strategies currently being used to treat HIV/AIDS.
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
6.
Is evolution by natural selection unidirectional and irreversible? Why or why not? Use evidence from the rise of AZT resistance to justify your answer.
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
7.
Describe the evidence supporting the hypothesis that AZT loses its effectiveness over time because HIV virions become resistant to its effects. Be sure to clearly identify the alternative hypothesis that was tested and how that hypothesis was refuted.
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
8.
What do the authors mean when they write that " . . . the HIV population in any particular host ultimately evolves itself right out of existence"? Explain how co-receptor switching is another example of "short-sighted evolution" in HIV populations within individual hosts. How can traits that seem to be unfavorable for an HIV population's long-term survival be maintained over evolutionary time?
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
9.
Define the term virulence. Describe Ewald's transmission rate hypothesis for the high virulence of HIV. Be sure your explanation addresses the "virulent" and "benign" strategies and their relative costs and benefits under different regimes of sexual behavior. Outline the two "natural experiments" currently underway to test this hypothesis, and state the specific outcomes the hypothesis predicts for each.
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
10.
Describe the evidence that mutations in the CCR5 gene confers resistance to HIV. What hypotheses have been proposed to explain the difference in the frequency of the delta-32 allele among human populations?
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
11.
Briefly describe how vaccines work and why understanding the evolutionary history of HIV is important in addressing the likelihood of developing a vaccine. What does recent analysis of the phylogeny of HIV tell us about its origin and history, and what does this suggest about the likelihood of developing a functional vaccine?
[Hint ]
To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
