Emphasizing Concepts in a Yeast Genetics Laboratory

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Categories: GSI Online LibraryTeaching Effectiveness Award Essays

by Elizabeth Shank, Molecular and Cell Biology

Teaching Effectiveness Award Essay, 2003

I experienced a teaching problem while leading my yeast genetics section of MCB110L. The students in the class met three times a week at mid-day for an hour of lecture, and then spent the rest of the afternoon performing experiments under my guidance. The lectures given by the professor were thorough in covering the background of the concepts behind the labs, but they did not discuss the experiments in any specific detail. The actual experiments were quite complicated, consisting of a number of non-obvious steps where the logic behind them was fairly involved. However, it was not necessary to understand the reasoning behind doing any single step, since the protocols in the laboratory manual made it easy to simply “follow the directions.” Because most of my students were reasonably adept at performing the mechanical aspects of each lab (or if not, they usually became so after a demonstration of the technique), it was all the more difficult to ensure that they understood why they were doing something.

In order to begin addressing this problem, I modified the requirements for their experimental flow-charts. Because multiple experiments were running simultaneously, some lasting a full five weeks, the students wrote up flow-charts outlining the course of each. Initially, they were only intended to cover the practical things to be done each day, facilitating the timely completion of their work. However, it had the unfortunate consequence of emphasizing mechanics over conceptual insight. I therefore asked that they begin to include a reason for each major step if they knew it, along with any key questions they had about the entire experiment. Since I reviewed the flow charts before handing them back, it allowed me to quickly learn what portions were the most baffling, and who in particular did not understand the concepts. I promptly expanded my usual pre-lab chalkboard talk from simply reviewing daily procedures and giving technical demonstrations to covering the most confusing ideas. On some days I ran an in-depth discussion, on others I provided handouts about some of the trickier logic, while on others I only alluded to why a procedure was critical. This meant that in addition to giving them more information, I also gave them a starting point for asking me questions. Because I now knew who did and did not comprehend the material, I could also address this problem by facilitating peer learning. During the class, I would typically move throughout the room, answering questions and correcting technique errors. Now, when students asked questions, rather than me directly explaining the reasoning, I could better use the other students around us, encouraging them to answer their fellow student’s question, while I merely made sure the information they provided was correct and complete, and assisted them if they became confused.

There were a few ways to assess whether these techniques had the desired result of helping students work through the logic of these experiments. To start, a number of short quizzes were given, and, with appropriate questions, it was possible to ascertain whether students were moving beyond a cursory understanding of the mechanics of the lab. In addition, I noticed a change as I casually asked students what they were doing: although they would frequently give the most direct answer of the technical step they were completing, some began describing it in terms of its broader purpose. Significantly, more students began feeling confident at explaining aspects of the lab to their peers when asked to do so, and often did so without my prompting or presence. I began to overhear students answering each other’s questions correctly, and address some of the points I had deliberately covered incompletely in my pre-lab discussions.