This would be a lot of fun. You can get some little Styrofoam balls that they sell at any store that has a arts and craft department. Pick like four colors you want to use for your DNA strand and paint the balls those colors. Let them dry and along with some toothpicks and some strong thread and a kneel to connect the ladder of balls together you can put it on a stand if you like, but you don’t have to. Now the real fun beginnings. With two of the colors start connecting the balls with the alternating the colors. threading the balls altogether when you are done you will use the toothpicks for the center balls and to stabilize your DNA strand and there, you go.