DNA. Conceptual model of deoxyribonucleic acid (DNA), the molecule that is the template for life. This model shows the two intertwining backbones of DNA as chains of phosphate groups (cyan) and sugars (black with white outline). The cross- linking bases are shown as horizontal rods, with the hydrogen bonds that bind them depicted as black spheres. DNA carries the instructions necessary for the growth and development of an organism. The sequences of the bases along the chains form recipes for proteins, the building blocks of living organisms. Sequences of DNA that code for specific proteins are known as genes.