A DNA sequence is a succession of letters representing the primary structure of a real or hypothetical DNA molecule or strand. The possible letters are A, C, G, and T, representing the four nucleotide subunits of a DNA strand, and typically these are printed abutting one another without gaps, as in the sequence AAAGTCTGAC. A succession of any number of nucleotides greater than four is liable to be called a sequence. With regard to its biological function, which may depend on context, a sequence may be sense or anti-sense (see DNA), and either coding or noncoding.

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