Third Position

                       A      C      G      U
                 _____________________________
             AA  |    Lys    Asn    Lys    Asn
        F    AC  |    Thr    Thr    Thr    Thr
        i    AG  |    Arg    Ser    Arg    Ser
        r    AU  |    Ile    Ile    MET    Ile
        s P  CA  |    Gln    His    Gln    His
        t o  CC  |    Pro    Pro    Pro    Pro
          s  CG  |    Arg    Arg    Arg    Arg
        & i  CU  |    Leu    Leu    Leu    Leu
          t  GA  |    Glu    Asp    Glu    Asp
        S i  GC  |    Ala    Ala    Ala    Ala
        e o  GG  |    Gly    Gly    Gly    Gly
        c n  GU  |    Val    Val    Val    Val
        o    UA  |     .     Tyr     .     Tyr
        n    UC  |    Ser    Ser    Ser    Ser
        d    UG  |     .     Cys    Trp    Cys
             UU  |    Leu    Phe    Leu    Phe


Another way to look at this is:

            3 Letter   1 Letter       DNA codons for each Amino Acids
NAME    Abbreviation  Abbreviation

Alanine         Ala       A 		GCA,GCC,GCG,GCU
Cysteine        Cys       C		UGC,UGU
Aspartic Acid   Asp       D		GAC,GAU
Glutamic Acid   Glu       E		GAA,GAG
Phenylalanine   Phe       F		UUC,UUU
Glycine         Gly       G		GGA,GGC,GGG,GGU
Histidine       His       H		CAC,CAU
Isoleucine      Ile       I		AUA,AUC,AUU
Lysine          Lys       K		AAA,AAG
Leucine         Leu       L		UUA,UUG,CUA,CUC,CUG,CUU
Methionine      Met       M		AUG
Asparagine      Asn       N		AAC,AAU
Proline         Pro       P		CCA,CCC,CCG,CCU
Glutamine       Gln       Q		CAA,CAG
Arginine        Arg       R		CGA,CGC,CGG,CGU
Serine          Ser       S		UCA,UCC,UCG,UCU,AGC,AGU
Threonine       Thr       T		ACA,ACC,ACG,ACU
Valine          Val       V		GUA,GUC,GUG,GUU
Tryptophan      Trp       W		UGG
Tyrosine        Tyr       Y		UAC,UAU

Stop Codons               .             UAA,UAG,UGA


An example of the multiple combinations of DNA possible for a single peptide
is an example of spelling my first name (without a termination codon):

So to code for 'MARK' there would be 16 combinations, other sequences of
4 letters would vary in the number of possibilities based on the number of
codons that could code for a single amino acid.  Some amino acids have
unto 6 codons that will be translated into a single Amino Acid.

 M   A   R   K    M   A   R   K    M   A   R   K    M   A   R   K 
MET Ala Arg Lys  MET Ala Arg Lys  MET Ala Arg Lys  MET Ala Arg Lys
===============  ===============  ===============  ===============
AUG-GCU-AGA-AAG  AUG-GCU-AGG-AAG  AUG-GCU-AGA-AAA  AUG-GCU-AGG-AAA
AUG-GCG-AGA-AAG  AUG-GCG-AGG-AAG  AUG-GCG-AGA-AAA  AUG-GCG-AGG-AAA
AUG-GCC-AGA-AAG  AUG-GCC-AGG-AAG  AUG-GCC-AGA-AAA  AUG-GCC-AGG-AAA
AUG-GCA-AGA-AAG  AUG-GCA-AGG-AAG  AUG-GCA-AGA-AAA  AUG-GCA-AGG-AAA