How to Make a DNA Double Helix Model

Written by susan king
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DNA, or deoxyribonucleic acid, is the basis of our chromosomes and the material that stores the information needed to build proteins to repair or grow cells, and the instructions for the traits we inherit from our parents. James Watson and Francis Crick discovered the double helix structure in 1953. They were awarded the Noble Prize for their discovery in 1962. You can build your own basic DNA model for better understanding the DNA that makes us each unique, and keeps our body systems running.

Skill level:
Moderately Challenging

Things you need

  • 20 1 1/2-inch styrofoam balls
  • 20 1-inch styrofoam balls
  • Styrofoam square
  • 2 long chenille stems
  • Toothpicks
  • 6 colours of non-acrylic paint
  • Wire coat hanger

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    Preparing the Balls

  1. 1

    Decide the colours for the components of the DNA. Paint 10 of the large 1 1/2 inch balls as the sugar molecules and 10 as the phosphate molecules.

  2. 2

    Divide the smaller 1 inch balls into 4 groups of 5 and paint as the nucleotide bases. These will be the adenine, cytosine, thymine and guanine bases. Paint the balls with a non-acrylic paint and allow to dry overnight.

  3. 3

    Check the balls for an even coating of the paint and that each ball is thoroughly dry before beginning to assemble the DNA model. ..

    Assembling the DNA

  1. 1

    Make two piles with the phosphate and the sugar balls. Alternate threading the balls on the long chenille stems in a sugar-phosphate pattern. Use 5 balls of sugar and 5 of phosphate on each stem. These are your outside uprights of the DNA ladder.

  2. 2

    Match the nucleotide balls together. Remember that adenine can be paired only with thymine, and cytosine only with guanine. Thread the balls in pairs on the toothpicks. Push the balls together in the centre of the toothpick, leaving the ends exposed to connect with the outside uprights of the DNA strand.

  3. 3

    Choose a nucleotide toothpick pair and push the exposed end of the toothpick into the first sugar molecule of the sugar-phosphate uprights. Add a drop of glue for stability. Repeat with the other end of the toothpick into the first sugar molecule of the other chenille upright. Remember to push the nucleotide pairs only into the sugar molecules, and not the phosphate.

  4. 4

    Continue adding nucleotide pairs to the strand until you run out of nucleotide pairs or room on the outside uprights. Research DNA patterns to make a specific DNA strand or randomly add the nucleotide pairs.

  5. 5

    Cut the wire hanger at each lower corner to give you a piece of wire about 12 inches long. Carefully thread the DNA strand on the wire by gently pushing the wire between the styrofoam balls of the nucleotide pairs. It is easiest to do this by laying the DNA strand flat on a smooth surface and holding it still while you thread the wire. Once threaded, you can twist the DNA gently to form the double helix shape. Stick one end of the wire into the styrofoam square so it stands upright. ..

Tips and warnings

  • You also can make the outside rungs of the DNA ladder with bamboo sticks, small dowel rods, pencils or wire, depending on the supplies you have available.
  • Be very careful when cutting the wire coat hanger. Have an adult supervise or help.
  • Acrylic paints will melt the styrofoam.

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