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Cool Tool: DNA Replication Zippers
Type: Model
Topic: DNA Replication
Grade Level: High School
Contributor: Jeanne Ting Chowning
School: BioLab, Seattle, WA
Purpose: To help students understand DNA replication through the use of a familiar analogy (the zipper).
Materials: Two identical white zippers that can unzip completely at the bottom. Four markers of different colors, e.g red, green, blue, yellow.
Methods: Prepare the zippers by coloring them with markers to show complementary bases. Each base is represented by a rectangle of a different color. For example, color a small rectangular area on one side of the zipper in green (representing T) and a rectangle on the opposite side of the zipper in yellow (representing A). Hydrogen bonds between bases are represented by the teeth of the zipper. Start the activity by showing the class one zipped zipper, holding it up so that all can see. Point out the four different bases and the hydrogen bonds (zipper teeth). Unzip to model DNA unwinding. Now zip each half of the zipper to the complementary half of the second zipper. The two halves of the second zipper represent newly synthesized DNA. At the end you will have two new double-stranded molecules that are identical to the starting zipper.
Classroom Use: Use when introducing DNA replication. This model shows how one strand of DNA can serve as the template for a new one. The semi-conservative nature of replication is also illustrated. Be sure to discuss limitations of the model (for example, both strands are synthesized in the same direction in the model).
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last updated 06/15/04