FALL 1998:

Imagine that, because of (or despite) your experiences in this class, you change your career choice and decide to become a doctor. You are admitted to medical school, pass with flying colors, and end up as a general practitioner with a thriving practice.

Questions 1 through 12 deal with one of your patients, a six-year-old girl from Thailand, who suffers from a chronic disorder called beta-thalassemia. Her symptoms include anemia (difficulty in transporting oxygen in the bloodstream), enlarged liver and spleen, bone malformations, and skin discoloration. She'll survive into young adulthood, but will require careful medical monitoring, drug therapy, and periodic blood transfusions throughout life.

1. Normal hemoglobin molecules are made up of four separate subunits, two of which are of a type called alpha-globin and two of which are of a type called beta-globin. Each of these subunits is a single peptide. This describes hemoglobin's
A. quaternary structure

2. What monomers make up each peptide?
D. amino acids

3. What is the name of the process in which each peptide is actually assembled, and where does this process take place?
C. translation, on ribosomes

4. Patients with beta-thalassemia produce defective beta-globin, or no beta-globin at all. This, of course, is because they have abnormal gene sequences that code for beta-globin. What are these variant gene sequences called?
E. alleles

5. Medical geneticists usually abbreviate the normal beta-globin gene as b, and the abnormal gene (in this case) as b⁰.

Neither of your patient's parents has beta-thalassemia. Which of these describes the most likely genotypes of both parents?
D. both are bb⁰ [Why? because if they have a kid with the disease, the kid must be b⁰b⁰ and must have received a b⁰ allele from each parent. Since neither parent has the disease, but both must have the bb⁰ allele, both must be bb⁰]

6. If your patient's parents decide to have another child, what is the chance that that child will also have beta-thalassemia?
A. 25%

7. Individuals who are heterozygous for the defective beta-globin gene (b⁰) often have a mild form of anemia, less serious than full-blown beta-thalassemia. This is an example of
B. incomplete dominance

8. For reasons not fully understood, individuals who are heterozygous for the b⁰ gene are also resistant to the infectious blood disease malaria. The b⁰ gene is most common in human populations native to malaria-prone parts of the world-such as southeast Asia, parts of Africa, and southeastern Europe. This pattern probably results from
D. natural selection

9. Malaria is caused by a single-celled organism called Plasmodium falciparum. P. falciparum has a nucleus. What taxonomic kingdom does it belong to?
B. Protista

10. The relationship between humans and Plasmodium falciparum is best described as
C. parasitism

11. One of the drugs that your patient will have to take is called desferrioxamine (trade name: Desferal). Desferrioxamine is produced naturally by an organism called Streptomyces pilosus. S. pilosus has no nucleus and no mitochondria. What taxonomic kingdom does it belong to?
A. Bacteria

FALL 2002:

On rocky coastlines of northern California, Oregon and Washington, you can find many kinds of invertebrates attached to the rocks, or living under them. One of them is Pisaster ochraceus, the orange starfish.

12. In the two-part Latin name of the orange starfish, the word Pisaster refers to the
A. genus.

13. Experiments in the 1960s showed that, if you remove Pisaster from a section of coast, a clam known as the blue mussel, which the starfish commonly feeds on, becomes so abundant that it overgrows everything else. Pisaster is an example of a/an
E. keystone species

14. Without Pisaster, mussel populations explode in size. For a while, at least, these populations undergo ________ growth.
C. exponential

15. Mussels are capable of growing in many parts of the shoreline. Normally, starfish, other predators such as gulls, and other living things on the rocks keep the mussels from living everywhere that they would be capable of living. This describes the mussels'
D. realized niche

16. When experiments were done on Pisaster starfish in the 1960s, one stretch of rocky coast had Pisaster removed, and another stretch was left alone. Why was one area of coastline left alone?
E. To act as a control.

17. Mussels belong to the phylum Mollusca. Which of the following is not a member of the Mollusca?
A. an earthworm [I didn't emphasize phylum names much in Spring 2004. . . I did mention this one, but if you have to prioritize what you're studying, this material's low priority.]

18. Suppose you could collect every starfish and every mussel from a stretch of coastline, weigh all the mussels together, and weigh all the starfish together. What would you predict your results would be?
C. The mussels would weigh about ten times as much as the starfish. [This is the "10% rule of thumb" for trophic pyramids]

19. Starfish belong to the phylum Echinodermata. Which of the following is a feature of Echinodermata?
C. five-part radial symmetry

This was just reported in the May 2003 issue of the magazine Scientific American: The biotechnology company VaxGen has just announced the results of its clinical trial of an HIV vaccine. If this vaccine works, injecting it into people will protect them from getting infected with HIV (human immunodeficiency virus), the cause of AIDS.

20. HIV is a retrovirus, which specifically means that it can
D. reverse transcribe its RNA to make a DNA molecule.

21. HIV is an exception to the Central Dogma of Molecular Biology, which may be summarized as:
E. DNA -> transcription -> RNA -> translation -> protein

22. When HIV reproduces, it frequently develops errors in its genetic material. Such "copying errors" are known as
B. mutations.

23. Inside the body of an HIV-infected person, a "struggle for existence" takes place. Some HIV viruses have "copying errors" in their genetic material that make them less likely to reproduce themselves. Others have "errors" that actually help them dodge the body's defenses, and make them more likely to reproduce. This creates a case of
A. natural selection.

24. A few scientists still do not believe that HIV causes the disease AIDS. Part of the reason for their skepticism is that HIV cannot be tested according to Koch's Postulates. Specifically,
C. it cannot be grown independently, outside the body of an infected person. [Some other answers are true statements about the virus, but this is the only answer that involves Koch's postulates.]

25. VaxGen's vaccine involved injecting people with a protein, called gp120, that is part of the outer coat of the virus. The gp120 protein enables HIV to stick to cells that it is about to invade. The protein can do what it does because of its
D. shape.

26. VaxGen tested its vaccine on 5000 sexually active gay men, in the United States and in Thailand, who volunteered for the clinical trial. Half of the men received injections of the vaccine, and the other half received injections of a placebo, which would be
E. something completely ineffective, such as plain water.

27. Neither the volunteers, nor the doctors who gave the injections, knew in advance who would get the real vaccine and who would get the placebo. A clinical trial that is done like this is called
E. double-blind.

28. There was no difference in HIV infection rates between those who received the vaccine and those who received the placebo. However, something unusual was observed: the vaccine seemed to be more effective in African, Asian, and Hispanic men than in men of European descent. Race may be an unexpected
B. variable.

29. In ecological terms, the relationship between humans and the HIV virus could be called
A. parasitism.
.

30. A virus very similar to HIV, called SIV (simian immunodeficiency virus), lives in African monkeys. Oddly, SIV doesn't make the monkeys sick. In ecological terms, the relationship between monkeys and the SIV virus could be called
D. commensalism.

31. Current HIV-fighting drugs, such as AZT and ddI, are chemically very similar to the monomers that make up DNA and RNA. However, they are different enough that, when they enter a cell, they "jam up" the cell's "machinery" and block the cell from making DNA and RNA. These monomers that make up DNA and RNA are called
C. nucleotides.

32. The monomers that make up DNA and RNA can further be divided up into
B. bases, phosphates and sugars.

SUMMER 2003:

These fourteen questions deal with advances in the treatment of bacterial infections.

33. A non-toxic antibiotic should be able to interfere with something that bacteria have, but that human cells do not have. Many antibiotics, such as penicillin, work in this way by interfering with bacterial
E. cell walls. [This is the only thing that bacteria have and that human cells don't have.]

34. Researchers studying bacteria could use Koch's postulates to
A. determine whether a bacterial species causes a particular disease.

35. Many bacteria produce exotoxins that cause illness. What is an exotoxin?
C. A poison that is released from the bacteria to travel through the body.

36. A bacterium called Clostridiuum botulinum produces a powerful exotoxin that happens to be a protein molecule. If you spill some of this exotoxin, you're supposed to pour some bleach on the spill. This neutralizes the toxin by causing its molecules to change shape, or in other word, to be
B. denatured. [I don't think I said much about this in Spring 2004, so if you guys miss this one, don't worry.]

37. Which of these statements gives an example of how natural selection contributes to the problem of antibiotic resistance?
B. Antibiotic-resistant bacteria tend to leave more offspring than others.

38. A new preventative treatment called probiotics is still in the experimental stage. The idea behind probiotics is that you infect someone with a harmless bacterium. If a harmful bacterium later invades that person's body, the harmless bacteria are supposed to out-compete the harmful ones. This is an example of
B. competitive exclusion.

39. If probiotics works, the harmless bacteria that were introduced into a person's body would theoretically be ___ on that person.
E. mutualistic

40. Another treatment called phage therapy, first developed in the Soviet Union in the 1930s, involves killing bacteria using a bacterium- infecting virus called a bacteriophage (or just phage for short). On the right is a diagram of a bacteriophage virus, shown in cross-section. The capsid is labeled B. #2. 41. A viral capsid is made up of C. proteins.

42. Since a bacteriophage is not a retrovirus, the stuff labeled #1 in the diagram is
D. DNA.

43. When a bacteriophage comes into contact with a bacterial host cell, the first thing that happens is
E. the phage injects its nucleic acid into the host cell.

44. Another experimental therapy involves molecules called cyclic D,L-alpha-peptides. These are polymers made up of
B. amino acids. [How do you know? You know because they're peptides. By definition, those are polymers of amino acids.]

45. A large number of individual cyclic D,L-alpha-peptide molecules can come together and assemble into a large tube-shaped protein molecule that can literally pierce a hole in a bacterium. This tubular shape is an example of
A. quaternary structure.

46. If you were participating in a clinical trial of cyclic D,L-alpha-peptides, you might have to get an injection of some sort. If neither you nor your doctor knew exactly what was in the injection, this would be
C. a double-blind experiment.

MISCELLANEOUS PRACTICE QUESTIONS ON ECOLOGY, FROM SEVERAL FINAL EXAMS:

47. In 1917, British botanist A. G. Tansley grew two different species of small herbaceous plants, the rock bedstraw (Galium saxatile) and the forest bedstraw (Galium sylvestre). When he grew each one singly, each species grew well. When he grew both together, one species always overgrew the other (which species overgrew the other depended on what type of soil he used). This experiment demonstrated
E. competitive exclusion

48. My nutrition-conscious mother says that eating cow liver is a bad idea, because you end up taking in all the toxins, heavy metals, pesticides, etc. that the cow's been exposed to. What ecological principle is she worried about?
C. biological magnification

49. At Glacier Bay, Alaska, a receding glacier leaves behind a bed of bare clay. The clay is colonized first by mosses and sedge grasses. These are replaced by shrubby willows, alder thickets, then by taller Sitka spruce trees, and finally, after about 100 years, by mixed spruce and hemlock. This is
B. primary succession [What makes it primary succession, rather than secondary succession, is the fact that it starts from a completely barren starting point that has never had life on it.]

50. Which of the communities listed in question 49 is the climax community?
D. mixed spruce and hemlock

51. What nutrient can be transferred from the air to the soil by an electrical discharge such as lightning?
E. nitrogen

52. In the wild, the American bald cypress tree, Taxodium distichum, grows best in very moist or even waterlogged soils (such as in swamps). It doesn't tolerate shade or harsh winters well, and so is not usually found north of the state of Delaware. These factors describe its
C. niche

53. Robins lay relatively large eggs, rich in nutrients. The parents incubate the eggs, and after hatching, bring food to the naked, helpless babies. This is an example of
A. K-selected life history

54. If you studied a large number of animals and plants in an area, along with the ways they were affected by their surroundings, you would be studying
D. an ecosystem

55. To raise enough beef to feed one person takes about 1.5 tons of corn and soybeans. The same amount of corn and soybeans, used as a direct food source, could support over 20 people for the same amount of time. Why is this the case?
C. Most of the available food energy is lost at each trophic level.

56. Which of these processes does not directly drive or affect the nitrogen cycle?
A. photosynthesis

57. On the island of Jamaica, there are many species of lizards that live on trees. They all feed on insects, but they don't compete with each other, because one species lives in high branches, one lives on small twigs, and one lives on the trunk. This state of affairs probably results from
B. niche partitioning

58. Which of these factors is most important in driving the hydrologic cycle?
D. evaporation and precipitation

59. Which of the following is an ecological decomposer?
E. A mushroom. [Because it's a fungus, and almost all fungi are ecological decomposers.]

60. Which of the following is a primary consumer?
C. A rabbit.