Name ______Date ______

Activity: Visualizing DNA

Goals: 1. To construct a paper model of a segment of DNA. 2. To show how the component parts of the DNA molecule “fit” together to make a ladder shape.

Background Information: The simplest form used to represent DNA – deoxyribonucleic acid - is a ladder shape. The ladder model can help us visualize how the components of the DNA molecule: the four different nitrogen bases and the sugar-phosphate sides pieces or backbones join together to form the complex structure of the “molecule of life.” The four nitrogen bases that make up the rungs of the DNA molecule are adenine, thymine, cytosine, and guanine. The nitrogen bases are abbreviated A, T, C, and G. It takes two nitrogen bases to make one DNA rung, and adenine always pairs with thymine and cytosine always pairs with guanine. Molecules of a sugar, ribose, and a phosphate form the side pieces, which make up the DNA “backbone.” If you could somehow twist this ladder model you’d be able to see that the true form of DNA is a twisted ladder or double helix.

Materials: Preprinted paper puzzle or cut-out shapes of the four nitrogen bases and sugar- phosphate sides on colored card stock paper, scissors, tape

1. What I Know: Write a sentence or two about what you already know about DNA.

2. Each student should cut out the following paper pieces to create the DNA paper model.

DNA Component Symbol Color Number of Pieces Sugar/phosphate pieces yellow/gold 12 Adenine Base A green 6 Thymine Base T purple 6 Cytosine Base C blue 6 Guanine Base G pink 6

3. Make a six “rung” DNA ladder by carefully attaching rungs and side pieces. Put the nitrogen base rungs together first, then add the sugar-phosphate side pieces. Use tape to attach all the pieces to one another. 4. Once you and your partner have completed your portion of the DNA model, attach your pieces together. Then add the segments from the other group members. 5. We will continue to attach all the segments until we create one long section of the DNA molecule. 6. Questions: a. Write a description of the DNA molecule based on your paper model. Describe how all the DNA components fit together with one another. Be as specific as possible.

b. How does DNA replicate?

c. Why is it important for the DNA molecule to replicate?