Final exam study guide: Practice exam 4

Here are some practice questions for the final exam. There are 30 questions, just like the real final, so I suggest you give yourself two hours to answer them. When you're done, you can see the answers.

  1. You want to know whether a common polymorphism (G or A in the DNA sequence) in the promoter of the uncoupling protein 2 gene is involved in type II diabetes. You measure the insulin sensitivity index (low values are associated with diabetes) in 5000 volunteers: 823 with the G/G genotype, 2732 with the G/A genotype, and 1545 with the A/A genotype. What test should you use?
  2. You want to know whether men who wear tight underwear have a higher proportion of female offspring than men who wear loose underwear. You search the literature and find 8 studies on this question, all of which seem like high quality, well designed studies. You combine the results of all of these studies, and men with tight underwear father 1.2 percent more female children than men with loose underwear. This combined result from all the studies has a P-value of 0.037. What is one reason why you might hesitate to reject the null hypothesis that underwear has no effect on sex ratio?
  3. You have taught your dog, Princess Fleabag, a new trick, balancing a doggie treat on her nose and catching it. You want to know whether the position of the treat on her nose affects her ability to catch it. You put the treat on the tip of her nose 20 times, and on the base of her nose, near her eyes, 20 times, and record how many times Princess Fleabag catches the treat from each position. What test should you use?
  4. You want to know whether prostate cancer cells that do not express active RhoC-GTPase adhere to bone marrow endothelial cells at the same rate as normal prostate cancer cells. You treat both kinds of cancer cells with a fluorescent substance and prepare a 24-well microtiter plate with endothelial cells in each well. You add the fluorescent cancer cells to the wells (12 wells with RhoC-GTPase- and 12 wells with RhoC-GTPase+ cells), wait half an hour, then wash away all the unattached cancer cells. You then measure the fluorescence in each well. What test should you use?
  5. You are a forensic entomologist, and you wonder whether animals who were on antibiotics will be colonized by different species of insects after they die than animals not on antibiotics. You get 11 pigs and put them on 11 different doses of tetracycline for a week, ranging from 0 to 100 mg/day. You kill the pigs and put them out in the woods for a week, then sample calliphorid fly maggots from each corpse and count the number in two species: Phaenicia regina and P. cuprina. The data range from 34% P. cuprina in the pig given 0 mg tetracycline to 60% P. cuprina in the pig given 100 mg tetracycline/day. Which test should you use?
  6. You are a walnut farmer, and you'd like to know whether fertilizing the soil around a tree affects the yield. You fertilize the soil around 50 walnut trees (randomly chosen throughout the orchard) and use 50 trees as the unfertilized control. For each tree, you count the number of walnuts it produces; because bigger trees will produce more walnuts, you also measure the diameter of each tree. Which test should you use?
  7. You've heard the saying "an apple a day keeps the doctor away," and you want to see if there really is an association between apple consumption and doctor visits. You find 250 volunteers who record how many apples they eat and how many times they go to the doctor for a year. Which test should you use?
  8. You want to know whether the gene that codes for mannose-6-phosphate isomerase (MPI) is expressed differently in liver tumors than in normal livers. You take biopsies from 27 normal livers and 32 cancerous livers and measure the amount of MPI mRNA in each one. Which test should you use?
  9. You want to know whether proximity of spicebush (Lindera benzoin) to black walnut (Juglans nigra) reduces the amount of herbivory on spicebush. Early in the spring, you plant 20 spicebush plants at various distances from a black walnut tree; at the end of the summer, you count the number of leaves with herbivore damage and the number undamaged by herbivores on each plant. Which test should you use?
  10. You are trying to model arm motions in a large number of people, and one of the important parameters is the flexion/extension moment arm of the bicep brachii muscle. It takes a lot of work to measure this accurately, but you think it might be possible to just measure the length of the ulna bone and estimate the flexion/extension moment arm from that. You take a small number of people and measure the length of the ulna bone and the size of the flexion/extension moment arm. Which test should you use?
  11. You want to know whether mice can see colors. Twenty times a day for two weeks, you put a piece of mouse food in a small red box and put it in a cage with one mouse. The mouse can tip the box over and get the food out. At the same time, you also put mouse food in a green box; it looks and smells the same as the red box, but is glued shut so the mouse can't get the food out. At the end of the two weeks, you put the two boxes in with the mouse for 10 more times. The mouse pushes over the red box first eight times and the green box two times. Which test should you use?
  12. You are studying the bacteria of Mono Lake, California, and you have found a strain of bacteria in the family Halomonadaceae that can survive in high concentrations of arsenic in the lab. You want to know whether these bacteria are a higher proportion of the bacterial community in areas with high concentrations of arsenic in nature. You collect sediment samples from different parts of Mono Lake and measure the arsenic concentration. Using one molecular probe that is specific to Halomonadaceae, and one that labels all bacteria, you count the number of Halomonadaceae cells and total number of bacterial cells in 1 microliter of each water sample. Which test should you use?
  13. You want to know whether the cover crop that is planted to keep soil from eroding in the winter affects the density of European corn borers in corn fields in the summer. In late September, in a field in Newark, you plant one acre with mustard, one acre with rye, one acre with clover, and one acre with turnips. In the spring you harvest these crops and plant corn, then in August you measure the number of European corn borers in each of five random 10 m2 sections of each field. Which test should you use?
  14. You want to know whether gulls have different food preferences. You go to the boardwalk at Rehoboth Beach and start tossing French fries into the air. You record how long it takes the first ring-billed gull to arrive and start grabbing fries out of the air. One hour later, you start tossing minnows into the air, and you record how long it takes the first gull to arrive. You repeat this 21 times for french fries and 12 times for minnow. Which test should you use?
  15. You want to know whether gramicidin affects sodium levels differently in different cell lines. You grow the cell line CAKI in two petri dishes, and you grow two petri dishes of HEK and two petri dishes of SLB. You treat one dish of each cell line with gramicidin and leave the other dish untreated, then measure the sodium level in 10 cells from each dish (one measurement per cell). Which test should you use?
  16. You want to know whether immunologically challenged sea urchin embryos and unexposed embryos differ in the length of the projections on their pigment cells. Each embryo has 10 to 15 pigment cells, and each pigment cell has 3 projections. You measure the length of all of the projections on all of the pigment cells from 5 immunologically challenged embryos and 5 unexposed embryos. Which test should you use?
  17. You want to know whether heterosexual couples are more likely to have the man sleeping on the right or the left side of the bed. You survey 1104 couples and ask each one whether the man slept on the right side or the left side of the bed the previous night. Which test should you use?
  18. You want to know whether the genotype at the phosphatidic acid phosphatase (HTPAP) gene is related to the probability of getting bladder cancer. You determine the genotype (GG, GC or CC) of 894 patients with urothelial bladder cancer, 555 patients with squamous cell bladder cancer, and 912 healthy controls. Which test should you use?
  19. You want to know whether Canada geese are more vigilant when they are standing on the edge of a flock, or in the middle. From an elevated platform, you take a picture of a flock of 600 geese standing on a lawn. You divide the flock into "edge" (within 2 meters of the outer perimeter of the flock) and "interior" (more than 2 meters from the edge). You count the number of geese being vigilant (having their head up, looking around) and the number of geese not being vigilant (with their head near the ground, looking for food) in the edge and interior. You do this for 10 more photographs of different flocks at different locations, all with about 300 to 800 geese in each flock. Which test should you use?
  20. You know that people with more flexible tendons, as measured by the shear modulus, have greater range-of-motion of their ankles. Now you want to know whether different tendon injuries affect range-of-motion. You get 20 volunteers with insertional Achilles tendinopathy, 30 with midportion tendinopathy, 15 with surgically repaired Achilles tears and 35 with Achilles tendinosis. You measure the shear modulus and range-of-motion of each person. Which test should you use?
  21. You want to test the effect of cocaine on running speed in mice. You add 15 micrograms/gram of cocaine to the food of 50 mice, you add 50 mg/g of sugar to the food of 50 mice, and you give regular food to 50 mice. After three days on these diets, you allow each mouse to run on a wheel and record its speed. You take five measurements of speed for each mouse. Which test should you use?
  22. You want to know whether sight or smell is more important for mice running a maze. You train 15 individually-numbered mice until they can successfully navigate a maze without making mistakes. You time each mouse as it runs the maze 5 times. Then you put blindfolds on each mouse and time it running the maze 5 times. Finally, you remove the blindfold and put noseplugs in the mouse's nostrils, and run each mouse through the maze 5 more times. Which test should you use?
  23. Your friend makes homemade whiskey, and she wants to know if aging it longer makes it taste better. In January, she prepares a large batch of whiskey and puts it into an oak barrel to age. She takes a sample from the barrel in February and lets you try it, then you try another sample every month for the rest of the year. After you have sampled the whiskey 11 times, you review your notes and put the samples in order from worst to best. Which test should you use?
  24. You want to know whether handedness (left or right handed) is associated with latitude. You go to 20 cities, from Quito, Ecuador (near the equator) to Fairbanks, Alaska, ask 200 people in each city whether they are right-handed or left-handed, and look up the latitude of each city. Which test should you use?
  25. You want to know whether honeybees collect more pollen per flight from peach, pear, apricot, or cherry. You put 5 honeybee hives in a peach orchard, 5 in a pear orchard, 5 in an apricot orchard, and 5 in a cherry orchard. At each hive, you capture 20 bees when they return from a foraging flight, scrape the pollen off each bee, and weigh each bee's pollen. Which test should you use?
  26. You want to know what affects sperm quality. You obtain semen samples from 100 rabbits, record the age, weight, and blood pressure of each rabbit, and examine about 50 sperm cells from each sample. You classify each sperm cell as either defective or normal. Which test should you use?
  27. You want to see if stem cell type affects their differentiation into cartilage cells. You take 750 embryonic stem cells and incubate them in dish of engineered hydrogel, and you incubate 750 adult stem cells in a dish of engineered hydrogel. After one week, you count the number of cartilage cells in each dish. Which test should you use?
  28. You want to know whether there's any truth to the urban legend that men with bigger feet also have bigger penises. You go to a nude beach and take a discrete (but still highly unethical) video of each man who walks down the beach, then you measure the length of each man's footprint in the wet sand. Later on, you watch all the videos; there's too much flopping around to accurately measure the penises from the videos, so you subjectively put the men in order, from smallest to largest penis. Which test should you use?
  29. Snail racing is a popular sport in Norfolk, England, and you want to know whether training makes a difference. You obtain 20 snails and measure their crawling speed. Then you train them for a week by giving them food every time they crawl quickly. At the end of the week, you measure the speed of each snail again. Then you stop training the snails, wait a week, and measure their speed again. Which test should you use?
  30. You want to know whether areas with lots of goldenrod plants are more likely to have a preying mantis. For each of 250 randomly placed 1-m2 plots in a field, you count the number of goldenrod plants. You also determine whether each plot has a praying mantis in it. None of the plots has more than one praying mantis. Which test should you use?

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