The three-dimensional structure of the self-complementary dodecamer d(CGCGAATTCGCG). The initial view in this ball-and-stick model is perpendicular to the helix axis. The sugar phosphate backbones (blue, with green ribbon outlines) wind around the periphery of the molecule. The bases (red) form hydrogen-bonded pairs that occupy the core. The two strands run in opposite directions. Click 'Label Bases' to label the nucleic acid building blocks in this dodecamer. Rotate the molecule to determine the number of hydrogen bonds associated with each base pair. [X-ray structure by Richard Dickerson and Horace Drew, UCLA. PDBid 1BNA. Drawing copyrighted © by Irving Geis.] See also Kinemage 2.1.