Exploring Bioethics - NIH Office of Science Education - National ...

6. Explain that each student should imagine that the envelopecontains information about his or her chance of gettingAlzheimer’s disease; students should pretend they have receivedtheir own personal genetic test results.17. Give each student a copy of Master 4.2: Alzheimer’s and GeneticTesting—Relevant Facts, and display the overhead transparencyof Part I of the master.8. Tell students that their “test results” contain information aboutthe gene for apolipoprotein E (APOE), found on chromosome 19,which is known to be a predictor of Alzheimer’s disease. Referringto the transparency, briefly instruct students about the differentvarieties of the APOE gene and how they affect lifetime chances ofcontracting Alzheimer’s disease. Suggest that students take noteson their copies of Master 4.2, as needed.You may want to draw on the following points, as well as the informationin Master 4.2, as you present information about the APOE gene:• The difference between the three varieties (alleles) of the APOEgene is only a single nitrogenous base; these are substitutionmutations. While E2 offers protection against developingAlzheimer’s disease, E4 increases a person’s chance of developing it.• The majority of humans have inherited a copy of E3 from each oftheir biological parents. This means that their APOE gene does notaffect their risk of developing Alzheimer’s disease.• Some people have inherited a copy of E4 from one parent, anda very small percentage (1 to 2 percent of the total population)has inherited a copy of E4 from both parents. People who haveinherited a copy of E4 from both parents have the greatestincreased chance of developing Alzheimer’s, as seen on the charton Master 4.2, Part I.• APOE results for the class reflect the distribution of the threeAPOE alleles in the human population as a whole. Just as only 1to 2 percent of the total human population has inherited two copies ofthe E4 version, the class should expect only one student’s envelopeto contain the slip of paper with E4/E4 on it. Most students whoopen their envelopes will find that they have inherited two copies ofthe E3 version.9. Explain that in a few minutes, students will choose whetherto open their envelopes. Tell them that before they make thatdecision, though, they need to gather more relevant, scientificinformation. Do not yet give permission for students to opentheir envelopes.2345Module 4 4-96