Constructing & Using Case Studies in Genetics to Engage Students in Active Learning

Article excerpt

[ILLUSTRATION OMITTED]

One of the national goals in science education is to teach science in a way that mirrors the process of science as inquiry, described by the National Science Education Standards (NSES) Science Teaching Standard B and Content Standard A (NRC, 1996). Inquiry-based learning, including the use of case studies, is one of several types of active learning that allows students to experience critical thinking skills inherent in the science process (Handelsman et al., 2007). Using case studies also develops skills in group learning and personalizes and humanizes science, making it more relevant to students (National Center for Case Study Teaching in Science, 2008). Case studies involving inherited conditions can be used to learn Medelian genetics in freshman or honors biology classes. Case studies can also serve as formative assessments to see how well students have learned and can apply genetic principles to real-world situations.

* Building a Case

The learning goals and the needs of the class should be taken into consideration when planning cases. For my lower level high school classes, cases are diagnostic and have one correct answer. The goal is for students to form hypotheses, apply their prior knowledge of Medelian genetics to analyze the information, and support their conclusions based on the data (Table 1).

Figure 1. An example of a case study in genetics with student
prompts.

A 27-year-old investment banker called his doctor concerned about
malodorous urine. When the patient urinated first thing that
morning, he had noticed that his urine had a terrible sulfurous
smell. It was now 10:00 am and his most recent urine still smelled.
The patient was concerned that he might have food poisoning. The
patient felt physically fine but was mentally distraught. He had
gone out to eat with his girlfriend the evening before to celebrate
her promotion. They drank a celebratory bottle of a new variety of
red wine that, in retrospect, seemed to have an off-taste. In
addition, the patient mentioned eating some foods for the first
time, such as artisanal cheeses made with raw milk, guava, star
fruit, asparagus, and parsnips. He had called his girlfriend but
she reported no change in the smell of her urine.

Working with your group, think of three possible reasons
(hypotheses) why this patient could be exhibiting these symptoms.

Describe how you would test each of the three hypotheses, including
any further information you would need.

[FIGURE 2 OMITTED]

A case opens with a scenario presenting information about an individual who is displaying unusual symptoms, along with prompts for student discussion (Figure 1). To promote thinking skills in students, I initially do not give them enough information to conclude whether the symptoms are from an inherited condition or due to other causes. Students propose hypotheses for the symptoms and how these could be tested.

Next, students are given a pedigree that shows the prevalence of the symptoms in the family of the individual (Figure 2). Students examine the pedigree and use the prompts to discuss their reasoning and conclusion about the type of inheritance depicted. Students often need to be reminded that even if the pedigree could support several modes of inheritance, they need to look at the prevalence of the trait in each generation.

Students want to know if the condition described in their case study is real or not. I either reveal the information or ask students to do some sleuthing for homework and report back to the class on their findings.

I use genetic conditions not usually found in biology textbooks that follow a single gene inheritance pattern. These conditions are not usually life-threatening and some may manifest later in life (Table 2), making for interesting cases. The National Center for Case Study Teaching in Science has many resources and links for designing or using existing case studies in all areas of science. …