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This article is about a notation method for the notation of genetic information. For multiple video card technology by Diamond Multimedia, see xDNA (multi-graphics). For other alternative nucleic acid coding systems, see nucleic acid analogues.

xDNA is a modified form of DNA with 8 nucleobases: the four natural bases A, C, G, and T, and four artificial modifications of these made longer by the addition of an extra benzene ring: xA, xC, xG, and xT.[1] A pairs with xT, C pairs with xG, G pairs with xC, and T pairs with xA, so the distance between the two halves of the double helix is consistently greater. The double helix is thus wider and has a longer pitch.

Experiments with xDNA are expected to provide new insight into the behavior of natural DNA. Also, the extended bases xA, xC, xG, and xT are fluorescent, and single strands composed of only extended bases can recognize and bind to single strands of natural DNA, which could make them useful tools for studying biological systems. The same research group also constructed widened DNA, called yDNA.

Chemical structure of dxA Chemical structure of dxT Chemical structure of dxC Chemical structure of dxG
Adenine Thymine Cytosine Guanine
Modified nucleobase dxA.svg Modified nucleobase dxT.svg Modified nucleobase dxC.svg Modified nucleobase dxG.svg
Size-expanded xA Size-expanded xT Size-expanded xC Size-expanded xG


  1. ^ Lynch, Stephen R.; Haibo Liu, Jianmin Gao, and Eric T. Kool (October 2006). "Toward a Designed, Functioning Genetic System with Expanded-Size Base Pairs: Solution Structure of the Eight-Base xDNA Double Helix". Journal of the American Chemical Society 128 (45): 14704–14711. doi:10.1021/ja065606n. PMC 2519095. PMID 17090058.