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
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Analogy and Gesture for Mental Visualization of DNA Structure Anveshna Srivastava and Jayashree Ramadas
Introduction The birth of molecular biology was significantly marked by the discovery of the double-helical structure of the DNA molecule by Watson and Crick (1953a). The general correctness of this structure was gradually proven in the subsequent years by substantial research on the structural as well as functional aspects of the DNA molecule. The structure of DNA had immediate functional implications: “It follows that in a long molecule many different permutations are possible, and it therefore seems likely that the precise sequence of the bases is the code which carries the genetical information” (Watson & Crick, 1953b, p. 965). Conceptual understanding in molecular biology involves integration of the macro (genetic traits), micro (cell), and molecular (gene) levels. Building up of the DNA molecular structure and its location at the cellular level leads to an understanding of its biological significance, for example, in genetic expression. Marbach-Ad and Stavy (2000) remarked that the difficulty in understanding and linking these different organizational levels is “because sometimes one level (e.g., the macro level) belongs to one discipline (e.g., biology), and the other level (e.g., the molecular level) belongs to different discipline (e.g., chemistry)” (p. 201). In fact, the integration occurs in multiple ways—one that includes concepts from various disciplines, another that involves the macro, micro, and the molecular levels, and finally, the structure-function linkages within and across these levels. Structural-functional linkages have been identified as a problem area in elementary genetics (Lewis, 2004; Marbach-Ad, 2001). In a study of major problem areas in biological sciences as identified by students, Bahar, Johnstone, and Hansell (1999) reported that the structure and function of the DNA and RNA molecule
A. Srivastava (*) • J. Ramadas Homi Bhabha Centre for Science Education, Tata Institute of Fundamental Research, Mankhurd, 400088 Mumbai, India e-mail: [email protected]; [email protected] D.F. Treagust and C.-Y. Tsui (eds.), Multiple Representations in Biological Education, Models and Modeling in Science Education 7, DOI 10.1007/978-94-007-4192-8_17, # Springer Science+Business Media B.V. 2013
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was considered as a topic of relatively low difficulty. However, we make a case here that students do have a problem in understanding the basic 3-D structure of the DNA molecule.
Structure of the DNA Molecule The double-helical structure of the DNA molecule can be visualized as two righthanded helices coiled around a central axis. Each helix is composed of a sugarphosphate backbone, and each (deoxyribose) sugar molecule in this backbone is attached with a nitrogenous base through a glycosidic bond to form a nucleoside unit. The nitrogenous bases—purines (adenine or guanine) or pyrimidines (thymine or cytosine)—are paired in a complementary fashion where ad
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