Deoxyribonucleic acid, more commonly known as DNA, is a fascinating aspect of life science. DNA has a remarkable molecular construction, which lends itself to an interesting and fun hands-on project, ideal for a biology science fair. Your double stranded model will demonstrate the basics of DNA, using different colors to indicate the six molecules that make up the DNA double helix.
Carry out background reading into the construction of DNA and how the studying of DNA has advanced since it was first discovered in 1952. Use your research from library articles, journals, books and the Internet to form the foundation of your project. Often, when presenting a double helix DNA model, you are expected to deliver a speech or presentation alongside the model.
Making the Molecules
Almost all double stranded DNA models are made using Styrofoam balls. Your model requires a total of 52 Styrofoam balls, but you should have at least 10 spares for any mistakes you make or damage you discover. Divide your balls into one group of 18 for pentose molecules; one group of 16 for phosphate molecules; two groups of five for cytosine and guanine molecules; and two groups of four for adenine and thymine molecules. Designate each molecule group a particular, distinctive color and paint your Styrofoam balls accordingly before leaving to dry.
Join your molecules together using toothpicks. In DNA, molecules come in specific pairs --- cytosine and guanine and adenine and thymine. You will have 17 layers in total. The bottom layer consists of a phosphate molecule on each end with cytosine and guanine in the middle --- this layer runs horizontal on your model. Connect this layer by pressing one end of a toothpick into a phosphate molecule and the other end into a cytosine molecule. Connect the cytosine to guanine using a second toothpick. Finish the layer by connecting the guanine to the phosphate on the other end. Every other layer in the model consists of a pair of phosphate molecules at each end, which you should attach to another pentose molecule using a single toothpick going vertically. Continue adding layers, remembering that you must alternate the order of the molecules within a layer each time. For example, if the previous layer was adenine then thymine the next layer with these two molecules is thymine then adenine.
Constructing a Double Helix
To introduce a double helix shape to your model, build it around a center structure. Many model makers use a wooden base with a long pole protruding upwards from the center. Twist your layers around this center pole, gluing or taping the toothpicks in the layers to it where necessary to help form the double helix shape (see Resources). Monster Guide advises that you introduce the twist when you are between four and five layers in from the bottom and finish the twist the same distance from the model's top. Look at pictures of other models and DNA posters to understand the double helix shape.
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