Analogy and Gesture for Mental Visualization of DNA Structure

In this chapter, we report five beginning undergraduate students' understanding of the 3-D structure of DNA, and the use of gesture and analogy to enhance their 3-D visualization of DNA structure. Through clinical interview-cum-teaching sessions we first recapitulated their background knowledge of basic biology and chemistry prerequisites. We then proceeded to a microgenetic study of the students’ understanding of DNA structure, in which we found that initially all of them interpreted their familiar textbook diagrams as 2-D structures rather than 2-D representations of the 3-D structures. We subjected video data of these interview-cum-teaching sessions to a microgenetic time-sequence analysis, where we identified episodes during which the students used multiple representations of DNA backbone and nitrogenous bases and showed positive, that is, 2-D to 3-D transitions, and “Aha!” moments. We traced these students’ learning episodes to their use of gesture in combination with character viewpoint simulation in terms of ladder analogy of the DNA molecule. Gesture, analogy, and mental simulation —involving changing the viewpoint of an observer—were found useful for linking together DNA’s multiple external representations into its integrated internal representation, and thus perhaps for bringing about the observer’s mental visualization of its 3-D structure.