You must type this and all other homework assignments. Do not e-mail the assignment to me; turn it in early (at 322 Wolf) for a foreseeable absence, or turn it in late after an unexpected absence from class.
1. Under certain conditions, animal cell lines can become "immortalized," meaning they will keep growing and dividing indefinitely in laboratory cultures. Nowak et al. (2004) looked at the effect of the pro-apoptotic protein Bax on immortalization of mouse muscle cells. They made mice without the Bax protein (Bax−/−), established cell lines from them, and compared them to cell lines from mice with the Bax protein (Bax+/− and Bax+/+). After 50 days, all 7 lines of Bax−/− cells were still growing, while only 3 out of 9 of the lines with Bax were growing. Test the data using all three tests of independence, and compare the results of the three tests.
2. McDonald (1989) collected amphipods (Platorchestia platensis) on a beach on Long Island, New York, and determined their genotype at the mannose-6-phosphate isomerase (Mpi) locus. Totalled across several dates, there were 1002 Mpi100/100, 1715 Mpi100/90, and 761 Mpi90/90 females; there were 676 Mpi100/100, 1204 Mpi100/90, and 442 Mpi90/90 males. Is the difference in genotype proportions between females and males significant? Test the data using the chi-squared and G-tests of independence, and compare the results of the two tests. Optional: If you want some extra fun, use SAS to analyze the data using Fisher's exact test, as well.
3. Plot the data from question 2 on a graph.
4. You have genetically engineered bacteria to produce the glue that mussels use to attach themselves to rocks, and you want to use this glue in dentistry. You're worried that it may cause gum inflammation, so you want to test it on the teeth of miniature pigs. You'll compare it to a control glue; based on previous work, you expect about 5 percent of the pigs with control glue to experience inflammation (you're just scoring pigs as "inflamed" or "not inflamed," not measuring the extent of inflammation). Before they'll approve this experiment, the university's Animal Care and Use Committee wants to know how many pigs you're going to use. Perform a power analysis and write a paragraph justifying your numbers and summarizing your results.
5. The Animal Care and Use Committee has told you that they'll only approve the experiment in question 4 with 10 control pigs and 10 mussel glue pigs. How small a difference in the proportion of pigs that are inflamed can you expect to detect?
McDonald, J.H. 1989. Selection component analysis of the Mpi locus in the amphipod Platorchestia platensis. Heredity 62: 243-249.
Nowak, J.A., J. Malowitz, M. Girgenrath, C.A. Kostek, A.J. Kravetz, J.A. Dominov, and J.B. Miller. 2004. Immortalization of mouse myogenic cells can occur without loss of p16INK4a, p19ARF, or p53 and is accelerated by inactivation of Bax. BMC Cell Biology 5:1.
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This page was last revised August 3, 2009. Its URL is http://udel.edu/~mcdonald/stathw3.html