Academic journal article The Science Teacher

Getting the Most out of Electrophoresis Units: Ideas for Using Electrophoresis Units to Teach a Variety of Science Concepts

Academic journal article The Science Teacher

Getting the Most out of Electrophoresis Units: Ideas for Using Electrophoresis Units to Teach a Variety of Science Concepts

Article excerpt

Do you look at those gel boxes gathering dust on prep room shelves and think about all the money invested in that once-a-year equipment typically used only by biology students? Or perhaps you wish you had some electrophoresis chambers, but your department does not see why they should allocate sparse resources for a single lab activity.

Gel electrophoresis units are a must-have piece of equipment for the required molecular biology laboratory for Advanced Placement (AP) Biology. However, the units can be used in other ways and in other laboratory settings. Because electrophoresis separates small amounts of nucleic acids or proteins with high resolution and sensitivity, it has many applications in modern bioscience experiments. Biology researchers use horizontal gel electrophoresis, vertical polyacrylamide gel electrophoresis, two-dimensional electrophoresis, and capillary electrophoresis. Therefore, it is valuable for science students to learn something about this key experimental tool.

Typically an electrophoresis chamber costs about $200, but you also need a power supply, which adds about $350. However, each power supply will run two to four chambers. If you pay a little more and select a power supply with continuously variable voltage that displays current output in milliamps as well as the customary voltage selector, the electrophoresis unit (chambers plus power supply) can become an even more versatile learning tool in chemistry and physics.

At Oklahoma City Community College, we have developed gel electrophoresis activities that support active learning of many scientific concepts including: pH, electrolysis, oxidation reduction, electrical currents, potentials, conductivity, molarity, gel electrophoresis, DNA and protein separation, and DNA fingerprinting. This article presents six different ways we use electrophoresis to help students learn multiple science concepts (Figure 1, p. 54). The activities mentioned in this article can be replicated using the protocols on our Biotechnology/ Bioinformatics Discovery! Project website (see "On the web" at the end of this article).

Deconstructing electrophoresis

We try to demystify electrophoresis for students by beginning with a "What goes on during electrophoresis?" activity (Figure 2, Part 1, p. 55). Students start with the empty gel box, rinsed well with distilled water. Focusing on what happens in the chamber without the customary gel, students add a bromothymol blue solution to the box and try to measure current flow when they connect the power supply to the chamber. Bromothymol blue is an indicator; it is yellow in acid, blue in base. A current is detected visually by the presence of bubbles arising from wells or by reading the milliamps value from the power supply. Next, students add a pinch of salt and the power is turned on again. Students observe that the current does not flow through the chamber in air alone, nor through dilute bromothymol blue and distilled water, but does flow with the addition of salt to the colored solution.

Moreover, the colors from the pH indicator show acid accumulation at one pole and base at the other. These observations of chamber events lead to discussions of current flow, pH, and conductivity. In a chemistry class, this same setup can be used to study the electrolysis of water and oxidation-reduction reactions (The Gene Connection 2007). To assess students as part of this exercise, ask them to hypothesize what might happen if a gel were prepared with distilled water instead of using a buffer. The correct student not only describes an unsatisfactory gel result, but uses the relative conductivity of distilled water versus buffer or salt solutions to justify the answer.

Another activity to help students understand electrophoresis is the simple, visual "Agarose gel electrophoresis with dyes" activity (Figure 2, Part 2, p. 56). For this activity, students practice loading samples and running agarose gels with inexpensive food dyes and observing the food dyes as they move at different speeds and in different directions through the gel due to molecular sizes and charges. …

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