A DNA sequence or genetic sequence is a succession of letters representing the
primary structure of a real or hypothetical
DNA molecule or strand, with the capacity to carry
information.The possible letters are A, C, G, and T, representing the four
nucleotide subunits of a DNA strand -
adenine,
cytosine,
guanine,
thymine bases covalently linked to phospho-backbone. In the typical case, the sequences are printed abutting one another without gaps, as in the sequence AAAGTCTGAC, going from 5' to 3' from left to right. 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, and either
coding or
noncoding. DNA sequences can also contain "
junk DNA."
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