Standard genetic code

The standard genetic code is the list of codons, made up of triplet bases on RNA, that provide instructions for which amino acid to add to a growing protein chain. The codon triplets are three sequential bases which can include adenine (A), cytosine (C), guanine (G) or uracil (U). The codon for the amino acid methionine is also the start codon in mRNA used to initiate protein production. These codons are made to interact with the corresponding anti-codon in transfer-RNA molecules (tRNA). Although some amino acids have only one codon, such as AUG for methionine, other amino acids are indicated by several codons. Thus, proline has four codons, CCU, CCC, CCA and CCG. This means there is a one-to-one correspondance in going from codon to amino acid, but not from an amino acid to codons. There is only one start codon, AUG, which serves as the codon for methionine, but there are three stop codons, UAA, UAG and UGA. The sequence of codons in mRNA is derived from the sequence present in the DNA from which the mRNA was transcribed.

UUU	Phe	UCU	Ser	UAU	TYR	UGU	Cys
UUC	Phe	UCC	Ser	UAC	Tyr	UGC	Cys
UUA	Leu	UCA	Ser	UAA	Stop	UGA	Stop
UUG	Leu	UCG	Ser	UAG	Stop	UGG	Trp
CUU	Leu	CCU	Pro	CAU	His	CGU	Arg
CUC	Leu	CCC	Pro	CAC	His	CGC	Arg
CUA	Leu	CCA	Pro	CAA	Gln	CGA	Arg
CUG	Leu	CCG	Pro	CAG	Gln	CGG	Arg
AUU	Ile	ACU	Thr	AAU	Asn	AGU	Ser
AUC	Ile	ACC	Thr	AAC	Asn	AGC	Ser
AUA	Ile	ACA	Thr	AAA	Lys	AGA	Arg
AUG	Met	ACG	Thr	AAG	Lys	AGG	Arg
GUU	Val	GCU	Ala	GAU	Asp	GGU	Gly
GUC	Val	GCC	Ala	GAC	Asp	GGC	Gly
GUA	Val	GCA	Ala	GAA	Glu	GGA	Gly
GUG	Val	GCG	Ala	GAG	Glu	GGG	Gly