The shotgun scanning code.

For each amino acid, the appropriate shotgun codon ideally encodes only the wild-type amino acid or alanine, but the nature of the genetic code necessitates the occurrence of 2 other amino acids for some shotgun substitutions. Single-letter amino acid and nucleotide abbreviations are used. *DNA degeneracies are represented by the IUB code (K = G/T, M = A/C, N = A/C/G/T, R = A/G, S = G/C, W = A/T, Y = C/T).