Candy can be made into a three-dimensional DNA model and afterward shared by all. Black and red licorice sticks and four different color gummy bears are cut into small pieces and threaded together with with fishing line by a needle. The red and black pieces are alternated with the different color gummy bears and twisted together in a helix. The red and black licorice represent sugar and phosphates of the DNA helix, while the different color gummy bears show the four bases of a DNA model.
Construction paper comes in many colors which is perfect for representing different parts of DNA. Pieces can be cut into shapes that signify the cytosine, guanine, adenine and thymine molecules of the helix with two pieces that fit together for the cytosine and guanine and two pieces that fit together for the adenine and thymine. A zipper like strand of paper is also cut and the pieces can fit into the grooves of it and be taped together.
DNA models can also made from Styrofoam balls. You can paint the balls with colors to represent the parts of the DNA helix being studied. The balls can be connected together at different angles with toothpicks. A pair of C-G (cytosine-guanine) balls can represent the first row be alternated with A-T (adenine-thymine) for the next.
Legos can be used to make perhaps the most accurate dimensional model by middle school students. The pieces all join together for a complex representation to look life-like. Legos are perfect because they come in different colors. Each colors can be a part of the DNA structure. Using Lego pieces, you can create a replica of the DNA double helix complete with four colored blocks to represent the four main bases of DNA.