X-Ray structure of a 10-bp RNA–DNA hybrid helix consisting of d(GGCGCCCGAA) in complex with r(UUCGGGCGCC). The structure is shown in stick form with RNA C cyan, DNA C green, N blue, and O red except for RNA O2', which is magenta, and P yellow. Click the "Show Backbone" button to view the sugar–phosphate backbone. Note that A-DNA-like helices are formed by both the RNA strand (cyan) and the DNA strand (green). [Based on an X-ray structure by Nancy Horton and Barry Finzel, Pharmacia & Upjohn, Inc., Kalamazoo, Michigan. PDBid 1FIX.]