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Cool 
Tool: DNA Beads
Type: Model
Topic: Complementary Base Pairing, Point Mutations, DNA Fingerprinting
Grade Level: High School
Contributor: Jeanne Ting Chowning
School: BioLab, Seattle, WA
Purpose: To teach DNA concepts, especially DNA fingerprinting.
Materials: Plastic or wooden craft beads (3/8 - 1/2 inch in diameter), colored red, green, blue, and yellow (or any four colors). Available at crafts stores.
Methods: Strings of colored beads are used to represent strands of DNA. Each color of bead represents one type of base. String the beads on a string that has been knotted in the middle. Then tie knots at each end. Use the central knot to lift the string, and the two complementary strands will hang down adjacent to each other. When making the strings, take care that when the DNA is "paired", the sequence of beads results in correct complementary base pairing. The incorrect pairing of one base/bead can be used to demonstrate the idea of a point mutation (have the students find the mismatch). Short repeated sequences of beads can represent DNA repeat segments that are used in DNA fingerprinting analysis. A short, second string of beads represents a DNA probe used in hybridization analysis. Hold the probe up to the longer strand to indicate the site of hybridization (make sure pairing is correct).
Classroom Use: DNA Beads are used in courtrooms to educate jurors but can also be used with success in the high school classroom. Use the beads in an introduction or review. DNA Beads also work well when used in conjunction with other models.
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last updated 06/15/04