The Nucleic acid nomenclature reference article from the English Wikipedia on 24-Apr-2004
(provided by Fixed Reference: snapshots of Wikipedia from wikipedia.org)

Nucleic acid nomenclature

Spread the word about a children's charity with social media
Molecular biologists use several shorthands when referring to nucleic acid molecules such as DNA and RNA, collectively referred to as nucleic acid nomenclature.

The most common is the representation of the base pairs as letters - an adenine nucleotide is abbreviated as A, guanine as G, cytosine as C, thymine as T, and in RNA, uracil as U.

Additionally the positions of the carbons in the ribose sugar that forms the backbone of the nucleic acid chain are numbered as follows:

Image:Nucleicacidnomenclature.png

Since the hydroxyl group attached to the 3' carbon of one base attaches to the phosphate group attached to the 5' carbon of the next base, 5' and 3' are often used to indicate the polarity of a DNA strand, e.g. "5' to 3'" and "3' to 5'". This is especially important as regards polymerization, where polymerization enzymes move exclusively from 5' to 3' along a DNA strand.