Modeling is a process used by scientists to assist in understanding the how the world works. Making models of molecules helps biologists and chemists define how the molecule is put together and predict the chemical nature of the molecule.
James Watson and Francis Crick used modeling, along with the X-ray crystallographic images of Rosalind Franklin, to determine the structure and nature of the DNA molecule.
I have devised a pattern that can be used to construct a paper model of the DNA molecule. This simple model helps students learn some(not all)of the properties of the construction of the molecule. In addition, the model shows off the beauty of the shape and symmetry of DNA. The patterns for the paper model can be obtained from my April 8 posts to this web site: www.cavalierscience.blogspot.com
First, the model illustrates that the DNA has two different, complementary sides. Second, that model shows that on one side, the sugar phosphate backbone of the molecule is bonded with the 5′ end going to the 3′ end, and the other side of the molecule is bonded with the 3′ end going to the 5′ end. Third, if students pay attention, when they are constructing the molecule, they will see that the Adenine base always pairs with the Thymine base and that the Cytosine base always pairs with the Guanine base. Lastly, students get a feel for how the helical shape comes about; the molecule fits in such a way that it has a natural twist. And there is more. When everyone’s model is made, the models can be taped together, end-to-end to illustrate that DNA is a very long twisted molecule.
After the paper model patterns are copied, they are cut out on all of the solid lines. The shaded areas in the pattern are discarded. The dotted lines allow for the bases to be folded to create the horizontal rungs of the DNA “ladder.” Transparent tape is used to tape together the bases (hydrogen bonds). One base is placed slightly on top and overlapping the other matching base, and then the tape is applied by wrapping it around both front and back. Once one pair has been put together, all of the other pairs must be put together in the same way. If this is done properly, the molecule will naturally twist into a perfect double helix. Copying the patterns onto colored paper adds interest and beauty to the model.
