Fall 2001 Physiology
1. One kind of male infertility occurs when there are small deletions in the Y chromosome which result in a smaller than usual number of sperm being produced -- not enough to ensure that sperm will reach and fertilize an egg. To treat this, Intracytoplasmic Sperm Injection (ICSI) is used, in which a single sperm is injected directly into the egg in the lab, then the fertilized egg is implanted in the mother. Some have criticized this technique, because the father's genetic defect would be passed on to the offspring, but prospective parents don't care; they just want a kid, and if their son turns out to have the same infertility, he can use the same technique to have his own kids. This month, scientists reported that these microdeletions imply an instability in the Y chromosome, and in some cells, the Y chromosome is so unstable that it is completely lost from the cell. When an XY baby is born to these men using ICSI, the baby may be a genetic mosaic, with most cells having the expected XY, but something like 10% of the cells having no Y chromosome at all.
Explain why babies born by ICSI have a greater than usual chance of having Turner's syndrome. Assume that the offspring is a genetic mosaic, in which some cells are XY and some have no Y. Your explanation should include a description of which are the embryonic cells that must have lacked the Y chromosome for Turner's syndrome to develop (5) AND draw a flowchart that summarizes the factors that are responsible for sexual differentiation at the level of the gonads (4), hormones (4), ducts (8), and external genitals (4) in this individual.
2. A patient, Ms. Terryess enters your office with somewhat mysterious symptoms: She has developed a painful stomach ulcer and has watery diarrhea. You suspect that she has Zollinger-Ellison syndrome, which results from a tumor of gastrin-secreting cells.
A. Her stomach contents are more acidic than usual. Why would this be compatible with the suggestion that she has Zollinger-Ellison? You can use a diagram or flowchart for your answer, provided it is well-labeled. (6)
B. You ask about her recent bowel movements, and she sounds amazed when she tells you that she noticed that the feces float on the surface of the water in the toilet bowl. You realize that this means that they have a high fat content. What is the mechanism by which an extremely high level of stomach acid leads to a lot of fat leaving the body in the feces? Your answer should include an explanation of what normally happens when gastric acid enters the intestines, and what would be altered if the gastric contents is super acidic. You can use a diagram or flowchart for your answer, provided it is well-labeled. (9 )
3. During finals week, the snack machines have a special discount on Voop!, a purplish drink made from the V. niko herb, which has the unusual ability to disable the valves in the veins.
A. After drinking Voop!, end diastolic volume will a. increase b. decrease(1). Explain why. Your answer should include an explanation of the role of valves and the meaning of end diastolic volume. 2 sentences is enough. (5)
B. To compensate for the effect of Voop!-ingestion, alpha and beta-1 receptors are stimulated. Explain where these receptors are and how stimulation of them will help to maintain a constant cardiac output, despite the change in EDV. Use formulas as appropriate. (8)
4. A pulse of ultrasound can kill the axons of neurons, but doesn't affect blood vessels. You apply ultrasound to the stalk connecting the pituitary gland to the hypothalamus of a rat that has recently been put in a stressful situation. Explain how this treatment will affect her ability to respond to the stress. Your explanation should include the various endocrine changes that occur in stress, and whether they would or wouldn’t be affected by the ultrasound treatment. (10)
5. Compare and contrast B and T cells. (12)
points for any 4)
Similarities:(4 points for any 2)
6. The editor of SELFISH magazine has asked you to write an article based on the scientific research of Randi Wolf and her colleagues, and she has a title picked out: Cheeseburgers and milkshakes - good for your bones? Your job is to summarize this research, which seems to suggest that high-fat foods may maximize calcium absorption. The young adult readers of this magazine have a short attention span, so you must keep your article to one side of a page. They’re not biology majors, so “translate” the scientific jargon into everyday English and describe only the most important details (3). Include an explanation of the roles of 1,25 dihydroxyvitamin D (4) and parathyroid hormone (4) in the body and suggest a physiological mechanism (4) that would explain why a low-fat/high-fiber diet might impair calcium absorption. Finally, explain to the readers at least two of the limitations of this study (10), based on any aspect of the experimental design, choice of subject, methods, or data analysis. (25 points total; about 10-15 sentences) (Advice: Jot notes on scrap paper while you read the article; Use these notes to write an outline that includes above points; Use this outline to write your essay.)