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Chapter 6 : DNA Structure
This chapter discusses the classroom activity regarding the visualization of the DNA structure. Having students assemble a model of DNA is probably the most useful way of communicating information about DNA structure to the large population of students who learn by doing. This has been successfully used in classroom settings ranging from junior high school/middle school to college. Advanced procedures, such as DNA sequencing and the polymerase chain reaction, depend on these differences, and students need to understand these aspects of DNA structure before they can understand the procedures. In a DNA molecule, two complementary DNA polymers are connected by the hydrogen bonds between the base pairs. The sugar-phosphate backbones of the polymers are oriented in opposite directions: one is 5' to 3', and the other is 3' to 5'. The two polymers (usually called strands) are twisted around each other to form the famous double helix. The double-helix structure of DNA is ideally suited to the cellular environment of the molecule. Hydrogen bonds "edges" of the base pairs are "visible" to cellular proteins between the spiraling strands of the sugar-phosphate backbone. DNA replication can be taught with this model by having students make extra nucleotides, simulate unwinding of the helix, and build new strands.