Genetics Teaching Vignettes: High School
Sickle Cell Anemia, A Case Study
Download: This vignette and all associated activities, masters, and worksheets can be downloaded in PDF at the GEP download page.
Instructional Materials (included at this website):
List of Classroom Activities:
Extending the analysis of blood and hemoglobin in the prelab activities, students view the three-dimensional structure of hemoglobin on the Internet. Students watch Blood is Life, a video that teaches about blood from the perspective of a young school teacher with sickle cell anemia. Students complete the Sickle Cell Anemia: Blood Video Questions and Translation Practice Worksheet, which reviews key concepts in the video and provides practice in conceptual transcription and translation of the b globin gene, both normal and mutant.
Sickle cell disease provides a clear example of how changes in DNA can result in an altered protein. Dry labs or exercises such as the Translation Practice Worksheet can be used to illustrate this connection. How can the disease be diagnosed? How can people with a family history of the disease learn whether they carry the trait? Discuss how the answers to these questions can be found by using restriction enzymes to analyze the DNA that codes for b globin and how hemoglobin itself can be analyzed by protein electrophoresis. Students can simulate a restriction analysis of wildtype and mutant b globin genes by eletrophoresing dyes through an agarose gel, as described in Sickle Cell Anemia: Diagnosis Using Simulated Restriction Analysis of DNA.
These activities lead naturally to the topic of genetic testing and a discussion of the ethical concerns that surround such testing. Use current newspaper and magazine articles related to genetics issues to get students thinking and stimulate discussion. Or watch one of several videos that deal with these issues, such as Children By Design, which includes segments on genetic testing, gene therapy, and medical selection of disease-free early embryos for implantation. To make decisions about genetics-related ethical issues, such as denying a person insurance coverage or employment based on his or her genotype, an ethical decision-making model like that developed by the Hastings Center can be used (see Appendix I and Cool Tools for a full description of the Hastings Center Model). In a role-playing activity that lets students practice their communications skills, students analyze prenatal karyotypes and write letters to the parents from the point of view of a doctor explaining the diagnosis and outlining the options. (Photographs of chromosome spreads for students to use in constructing karyotypes can be found in many biology textbooks and lab manuals or on the Internet; see Other Materials.) Note that because sickle cell anemia is not caused by a chromosomal abnormality, another genetic condition (e.g. Down syndrome) should be chosen for this activity.
Sickle cell anemia, which is inherited as an autosomal codominant, also provides the opportunity to discuss classical Mendelian genetics. Further connections can be made to meiosis, gamete formation, and environmental influences that can affect phenotype. Lastly, sickle cell anemia provides an outstanding opportunity to build a connection between genetics and evolution. Students learn the mechanisms by which allele frequencies in a population change over time in response to selective forces (such as malaria) by using laboratory simulations and analyzing disease distribution data. In the Allele Frequencies and Sickle Cell Anemia Lab (Appendix II), students randomly draw red and white beans from "gene pool" containers to model the changes in b globin allele frequencies in a population in response to the selective pressure of malaria.
Classical Genetics/Central Dogma:
*Note: American Biology Teacher has agreed to send out reprints of these articles upon request. To contact ABT, visit their website at: http://www.nabt.org/publications_journals.html.
Last updated 02/03/03