DNA Modeling Activity

Developed by the Science Museum of Minnesota, Susan Fleming

Materials:

• modeling clay (golf ball size)
• pipe cleaners (two per person)
• plastic straws (two per person)
• pipe cleaner cut into 2 inch pieces (six per person)
• plastic straws cut into 1.5 inch pieces (six per person)
• 10-20 beads (4 different colors)

Directions:

1. Slide the small straw pieces over each two-inch piece of pipe cleaner. Both ends of the pipe cleaner should stick out.
   
   The structure of DNA is like a twisted ladder and the pipe cleaners/straws will make up the rungs of this ladder.
   
   
2. Assign a chemical name to the four different colors of beads. One color should represent the chemical base A (adenine), another color for T (thymine), a different color for G (guanine) and C (cytosine).
   
   In double stranded DNA, A is always paired with T, and G is always paired with C. These two base pairs are always found across from each other on opposite sides of the ladder or two DNA strands.
   
   
3. Slide your beads onto open ends of the small pipe cleaners/straws. Pair your beads so that A is always across from T, and G is always across from C.
4. Attach the bead end of each rung to the two long pieces of pipe cleaner making a structure that resembles a ladder.
   
   The two long pieces of pipe cleaner represent the backbone of the DNA ladder. This backbone is composed of chemicals (phosphates and sugars) linked together to form a very long chain. The chemical bases are hung from the backbone like beads on a string.
   
   
5. Flatten the modeling clay to create a base for the DNA molecule. Push the ends of the two pipe cleaners into the base so that the structure stands up.
6. Crimp the end of one straw and slide this end into the open end of the other straw. Push the two straws together until they overlap about a half an inch.
7. Center the straw into the middle of the DNA model. Push the straw into the clay so that the straw helps support the DNA structure. Give the model a twist and tape in place. This helps to demonstrate that DNA has a twisted or helical structure.

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