|
DNA - The Code of Life - Deoxyribonucleic Acid, or DNA, is the molecule that stores genetic information about every living thing on Earth. DNA is made up of nucleotides, each of which is composed of a phosphate group, a five-carbon sugar (deoxyribose), and an organic, nitrogen containing base. The phosphate group (yellow ball with red balls attached), alternating with the sugar (gray balls), forms the outside rails of the helix. Connecting the two rails are the four different base pairs, Adenine, which pairs with Thymine, and Cytosine which pairs with Guanine. To produce the bottom and middle images, thin strands of crystalline DNA were X-rayed to create a diffraction pattern. By measuring the spacing on this pattern, scientists are able to determine the spacing between the nucleotides and the width of the helix. The bottom image was created using a program called Macmol on the Macintosh. The middle image was processed through an Evans and Sutherland PS390 stereographics machine and then refined and visualized on an SGI R4K Indigo Elan using a molecular surface rendering program. The surface is color coded by curvature, blue = convex, gray = concave, and white = flat. Note the deep minor groove, which is the width of a water molecule, compared to the wide, almost flat major groove.
|
