A DNA model has three key pieces: phosphates, ribose sugars and nucleotides. The nucleotides are subdivided into four separate bases: adenine, guanine, cytosine and thymine. In total, the DNA model should use six different colors of construction paper. However, which color stands for which component is up to you or your students. If you are using the DNA model as an art project for young students, assigning a specific pattern is best. If you are using the DNA model for high school students, you can allow the students to use whatever colors they choose as long as they provide a key. This has the benefit of checking to see if the students understand what components bind together in what order.
Construction paper has one unique advantage over any other DNA model medium: limitless shapes. When working with paper models, many teachers use puzzle pieces because this seems the most logical. Three-dimensional models fit together in an orderly manner so that it can support its weight and shape, but a two-dimensional model does not need to do that. Young or old, students would rather cut out stars, circles, triangles, squares and pentagons than curvy, crazy puzzle pieces. Print or draw the shapes onto a sheet of white paper and copy them to the construction paper to facilitate the model making.
If you are assigning a construction paper model to be graded, it is probably best to ask the students to glue the pieces to another sheet of paper. However, if you are using the DNA model as a hands-on illustration, staples will be easier and string will be more fun. Attaching DNA molecule pieces with staples is probably the most expedient method if you want the model to be free hanging. However, by using 2-inch or larger pieces, you can punch holes in either end and then tie the paper together with short pieces of yarn. Attach long pieces of yarn to the top of the DNA model to hang around the room as scientific mobiles.
A DNA model made from construction paper does not need to be flimsy. Even paper models can become sculptural. Two dowel rods can serve as the legs of the DNA ladder. Create a paper wrapped dowel rod by gluing or taping the phosphate and ribose sugar components around the dowel rod. Alternatively, you can connect each of the pieces first and then glue the dowel rod to the pieces without wrapping the rod entirely. Press the dowel rods into foam blocks or cups to serve as a base.