DNA is a long, double-stranded molecule twisted into a helix. It is composed of a chemical code (represented by the letters A, T, G, and C) that describes how to make proteins.
Image use policy: For non-commercial, educational purposes, this image may be used with a Creative Commons CC BY-NC-SA 4.0 license. Please credit as follows: © University of California Museum of Paleontology, Understanding Evolution, www.understandingevolution.org
This image is part of a series: