Single Letter Codes for Nucleotides
Nucleotide(s) Code Acceptable by Treated as
(in alignment)
makeblastdb/formatdb BLAST
A, CM (amino)-+N
A, GR (purine)-+N
A, TW (weak)-+N
C, GS (strong)-+N
C, TY (pyrimidine)-+N
G, TK (keto)-+N
A,C,GV (not T)-+N
A,C,TH (not G)-+N
A,G,TD (not C)-+N
C,G,TB (not A)-+N
A,C,G,TN (any nucleotide)++N
Universal Genetic Code
1st Pos Second Position 3rd Pos
TTTT (Phe, F)TCT (Ser, S) TAT (Tyr, Y)TGT (Cys, C)T
TTC (Phe, F)TCC (Ser, S) TAC (Tyr, Y)TGC (Cys, C)C
TTA (Leu, L)TCA (Ser, S) TAA (Ter, *)TGA (Ter, *)A
TTG (Leu, L)TCG (Ser, S) TAG (Ter, *)TGG (Trp, W)G
CCTT (Leu, L)CCT (Pro, P) CAT (His, H)CGT (Arg, R)T
CTC (Leu, L)CCC (Pro, P) CAC (His, H)CGC (Arg, R)C
CTA (Leu, L)CCA (Pro, P) CAA (Gln, Q)CGA (Arg, R)A
CTG (Leu, L)CCG (Pro, P) CAG (Gln, Q)CGG (Arg, R)G
AATT (Ile, I)ACT (Thr, T) AAT (Asn, N)AGT (Ser, S)T
ATC (Ile, I)ACC (Thr, T) AAC (Asn, N)AGC (Ser, S)C
ATA (Ile, I)ACA (Thr, T) AAA (Lys, K)AGA (Arg, R)A
ATG (Met, M)ACG (Thr, T) AAG (Lys, K)AGG (Arg, R)G
GGTT (Val, V)GCT (Ala, A) GAT (Asp, D)GGT (Gly, G)T
GTC (Val, V)GCC (Ala, A) GAC (Asp, D)GCC (Gly, G)C
GTA (Val, V)GCA (Ala, A) GAA (Glu, E)GGA (Gly, G)A
GTG (Val, V)GCG (Ala, A) GAG (Glu, E)GGG (Gly, G)G
NOTEMany organisms use alternative initiation and termination codons. The information is summarized in different translation tables and is available at this page.

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