DNA and RNA codon tables

The standard RNA codon table organized in a wheel

A codon table can be used to translate a genetic code into a sequence of amino acids. The standard genetic code is traditionally represented as an RNA codon table, because when proteins are made in a cell by ribosomes, it is messenger RNA (mRNA) that directs protein synthesis. The mRNA sequence is determined by the sequence of genomic DNA. In this context, the standard genetic code is referred to as translation table 1. It can also be represented in a DNA codon table. The DNA codons in such tables occur on the sense DNA strand and are arranged in a 5′-to-3′ direction. Different tables with alternate codons are used depending on the source of the genetic code, such as from a cell nucleus, mitochondrion, plastid, or hydrogenosome.

There are 64 different codons in the genetic code and the below tables; most specify an amino acid. Three sequences, UAG, UGA, and UAA, known as stop codons, do not code for an amino acid but instead signal the release of the nascent polypeptide from the ribosome. In the standard code, the sequence AUG—read as methionine—can serve as a start codon and, along with sequences such as an initiation factor, initiates translation. In rare instances, start codons in the standard code may also include GUG or UUG; these codons normally represent valine and leucine, respectively, but as start codons they are translated as methionine or formylmethionine.

The first table—the standard table—can be used to translate nucleotide triplets into the corresponding amino acid or appropriate signal if it is a start or stop codon. The second table, appropriately called the inverse, does the opposite: it can be used to deduce a possible triplet code if the amino acid is known. As multiple codons can code for the same amino acid, the International Union of Pure and Applied Chemistry's (IUPAC) nucleic acid notation is given in some instances.

Translation table 1

Standard RNA codon table

Amino-acid biochemical properties

Nonpolar

Polar

Basic

Acidic ↓

Termination: stop codon *

Initiation: possible start codon

Standard genetic code

1st base	2nd base								3rd base
	U		C		A		G
U	UUU	(Phe/F) Phenylalanine	UCU	(Ser/S) Serine	UAU	(Tyr/Y) Tyrosine	UGU	(Cys/C) Cysteine	U
	UUC		UCC		UAC		UGC		C
	UUA	(Leu/L) Leucine	UCA		UAA	Stop (Ochre) *	UGA	Stop (Opal) *	A
	UUG		UCG		UAG	Stop (Amber) *	UGG	(Trp/W) Tryptophan	G
C	CUU		CCU	(Pro/P) Proline	CAU	(His/H) Histidine	CGU	(Arg/R) Arginine	U
	CUC		CCC		CAC		CGC		C
	CUA		CCA		CAA	(Gln/Q) Glutamine	CGA		A
	CUG		CCG		CAG		CGG		G
A	AUU	(Ile/I) Isoleucine	ACU	(Thr/T) Threonine	AAU	(Asn/N) Asparagine	AGU	(Ser/S) Serine	U
	AUC		ACC		AAC		AGC		C
	AUA		ACA		AAA	(Lys/K) Lysine	AGA	(Arg/R) Arginine	A
	AUG	(Met/M) Methionine	ACG		AAG		AGG		G
G	GUU	(Val/V) Valine	GCU	(Ala/A) Alanine	GAU	(Asp/D) Aspartic acid ↓	GGU	(Gly/G) Glycine	U
	GUC		GCC		GAC		GGC		C
	GUA		GCA		GAA	(Glu/E) Glutamic acid ↓	GGA		A
	GUG		GCG		GAG		GGG		G

Inverse RNA codon table

Standard DNA codon table

Amino-acid biochemical properties

Nonpolar

Polar

Basic

Acidic ↓

Termination: stop codon *

Initiation: possible start codon

Standard genetic code

1st base	2nd base								3rd base
	T		C		A		G
T	TTT	(Phe/F) Phenylalanine	TCT	(Ser/S) Serine	TAT	(Tyr/Y) Tyrosine	TGT	(Cys/C) Cysteine	T
	TTC		TCC		TAC		TGC		C
	TTA	(Leu/L) Leucine	TCA		TAA	Stop (Ochre) *	TGA	Stop (Opal) *	A
	TTG		TCG		TAG	Stop (Amber) *	TGG	(Trp/W) Tryptophan	G
C	CTT		CCT	(Pro/P) Proline	CAT	(His/H) Histidine	CGT	(Arg/R) Arginine	T
	CTC		CCC		CAC		CGC		C
	CTA		CCA		CAA	(Gln/Q) Glutamine	CGA		A
	CTG		CCG		CAG		CGG		G
A	ATT	(Ile/I) Isoleucine	ACT	(Thr/T) Threonine	AAT	(Asn/N) Asparagine	AGT	(Ser/S) Serine	T
	ATC		ACC		AAC		AGC		C
	ATA		ACA		AAA	(Lys/K) Lysine	AGA	(Arg/R) Arginine	A
	ATG	(Met/M) Methionine	ACG		AAG		AGG		G
G	GTT	(Val/V) Valine	GCT	(Ala/A) Alanine	GAT	(Asp/D) Aspartic acid ↓	GGT	(Gly/G) Glycine	T
	GTC		GCC		GAC		GGC		C
	GTA		GCA		GAA	(Glu/E) Glutamic acid ↓	GGA		A
	GTG		GCG		GAG		GGG		G

Inverse DNA codon table

Alternative codons in other translation tables

The genetic code was once believed to be universal: a codon would code for the same amino acid regardless of the organism or source. However, it is now agreed that the genetic code evolves, resulting in discrepancies in how a codon is translated depending on the genetic source. For example, in 1981, it was discovered that the use of codons AUA, UGA, AGA and AGG by the coding system in mammalian mitochondria differed from the universal code. Stop codons can also be affected: in ciliated protozoa, the universal stop codons UAA and UAG code for glutamine. The following table displays these alternative codons.

Amino-acid biochemical properties

Nonpolar

Polar

Basic

Acidic ↓

Termination: stop codon *

Comparison between codon translations with alternative and standard genetic codes

Code	Translation table	DNA codon involved	RNA codon involved	Translation with this code			Standard translation	Notes
Standard	1							Includes translation table 8 (plant chloroplasts).
Vertebrate mitochondrial	2	AGA	AGA	Stop *			Arg (R)
		AGG	AGG	Stop *			Arg (R)
		ATA	AUA	Met (M)			Ile (I)
		TGA	UGA	Trp (W)			Stop *
Yeast mitochondrial	3	ATA	AUA	Met (M)			Ile (I)
		CTT	CUU	Thr (T)			Leu (L)
		CTC	CUC	Thr (T)			Leu (L)
		CTA	CUA	Thr (T)			Leu (L)
		CTG	CUG	Thr (T)			Leu (L)
		TGA	UGA	Trp (W)			Stop *
		CGA	CGA	absent			Arg (R)
		CGC	CGC	absent			Arg (R)
Mold, protozoan, and coelenterate mitochondrial + Mycoplasma / Spiroplasma	4	TGA	UGA	Trp (W)			Stop *	Includes the translation table 7 (kinetoplasts).
Invertebrate mitochondrial	5	AGA	AGA	Ser (S)			Arg (R)
		AGG	AGG	Ser (S)			Arg (R)
		ATA	AUA	Met (M)			Ile (I)
		TGA	UGA	Trp (W)			Stop *
Ciliate, dasycladacean and Hexamita nuclear	6	TAA	UAA	Gln (Q)			Stop *
		TAG	UAG	Gln (Q)			Stop *
Echinoderm and flatworm mitochondrial	9	AAA	AAA	Asn (N)			Lys (K)
		AGA	AGA	Ser (S)			Arg (R)
		AGG	AGG	Ser (S)			Arg (R)
		TGA	UGA	Trp (W)			Stop *
Euplotid nuclear	10	TGA	UGA	Cys (C)			Stop *
Bacterial, archaeal and plant plastid	11							See translation table 1.
Alternative yeast nuclear	12	CTG	CUG	Ser (S)			Leu (L)
Ascidian mitochondrial	13	AGA	AGA	Gly (G)			Arg (R)
		AGG	AGG	Gly (G)			Arg (R)
		ATA	AUA	Met (M)			Ile (I)
		TGA	UGA	Trp (W)			Stop *
Alternative flatworm mitochondrial	14	AAA	AAA	Asn (N)			Lys (K)
		AGA	AGA	Ser (S)			Arg (R)
		AGG	AGG	Ser (S)			Arg (R)
		TAA	UAA	Tyr (Y)			Stop *
		TGA	UGA	Trp (W)			Stop *
Blepharisma nuclear	15	TAG	UAG	Gln (Q)			Stop *	As of Nov. 18, 2016: absent from the NCBI update. Similar to translation table 6.
Chlorophycean mitochondrial	16	TAG	UAG	Leu (L)			Stop *
Trematode mitochondrial	21	TGA	UGA	Trp (W)			Stop *
		ATA	AUA	Met (M)			Ile (I)
		AGA	AGA	Ser (S)			Arg (R)
		AGG	AGG	Ser (S)			Arg (R)
		AAA	AAA	Asn (N)			Lys (K)
Scenedesmus obliquus mitochondrial	22	TCA	UCA	Stop *			Ser (S)
		TAG	UAG	Leu (L)			Stop *
Thraustochytrium mitochondrial	23	TTA	UUA	Stop *			Leu (L)	Similar to translation table 11.
Pterobranchia mitochondrial	24	AGA	AGA	Ser (S)			Arg (R)
		AGG	AGG	Lys (K)			Arg (R)
		TGA	UGA	Trp (W)			Stop *
Candidate division SR1 and Gracilibacteria	25	TGA	UGA	Gly (G)			Stop *
Pachysolen tannophilus nuclear	26	CTG	CUG	Ala (A)			Leu (L)
Karyorelict nuclear	27	TAA	UAA	Gln (Q)			Stop *
		TAG	UAG	Gln (Q)			Stop *
		TG	UGA	Stop *	or	Trp (W)	Stop *
Condylostoma nuclear	28	TAA	UAA	Stop *	or	Gln (Q)	Stop *
		TAG	UAG	Stop *	or	Gln (Q)	Stop *
		TGA	UGA	Stop *	or	Trp (W)	Stop *
Mesodinium nuclear	29	TAA	UAA	Tyr (Y)			Stop *
		TAG	UAG	Tyr (Y)			Stop *
Peritrich nuclear	30	TA	UAA	Glu (E) ↓			Stop *
		TAG	UAG	Glu (E) ↓			Stop *
Blastocrithidia nuclear	31	TAA	UAA	Stop *	or	Glu (E) ↓	Stop *
		TAG	UAG	Stop *	or	Glu (E) ↓	Stop *
		TGA	UGA	Trp (W)			Stop *
Cephalodiscidae mitochondrial code	33	AGA	AGA	Ser (S)			Arg (R)	Similar to translation table 24.
		AGG	AGG	Lys (K)			Arg (R)
		TAA	UAA	Tyr (Y)			Stop *
		TGA	UGA	Trp (W)			Stop *

See also

• Bioinformatics
• List of genetic codes

Further reading

• Chevance FV, Hughes KT (2 May 2017). "Case for the genetic code as a triplet of triplets". Proceedings of the National Academy of Sciences of the United States of America. 114 (18): 4745–4750. doi:10.1073/pnas.1614896114. JSTOR 26481868. PMC 5422812. PMID 28416671.
• Dever TE (29 June 2012). "A New Start for Protein Synthesis". Science. American Association for the Advancement of Science. 336 (6089): 1645–1646. Bibcode:2012Sci...336.1645D. doi:10.1126/science.1224439. JSTOR 41585146. PMID 22745408. S2CID 44326947. Retrieved 17 October 2020.
• Gardner RS, Wahba AJ, Basilio C, Miller RS, Lengyel P, Speyer JF (December 1962). "Synthetic polynucleotides and the amino acid code. VII". Proceedings of the National Academy of Sciences of the United States of America. 48 (12): 2087–2094. Bibcode:1962PNAS...48.2087G. doi:10.1073/pnas.48.12.2087. PMC 221128. PMID 13946552.
• Nakamoto T (March 2009). "Evolution and the universality of the mechanism of initiation of protein synthesis". Gene. 432 (1–2): 1–6. doi:10.1016/j.gene.2008.11.001. PMID 19056476.
• Wahba AJ, Gardner RS, Basilio C, Miller RS, Speyer JF, Lengyel P (January 1963). "Synthetic polynucleotides and the amino acid code. VIII". Proceedings of the National Academy of Sciences of the United States of America. 49 (1): 116–122. Bibcode:1963PNAS...49..116W. doi:10.1073/pnas.49.1.116. PMC 300638. PMID 13998282.
• Yanofsky C (9 March 2007). "Establishing the Triplet Nature of the Genetic Code". Cell. 128 (5): 815–818. doi:10.1016/j.cell.2007.02.029. PMID 17350564. S2CID 14249277.
• Zaneveld J, Hamady M, Sueoka N, Knight R (28 February 2009). "CodonExplorer: An Interactive Online Database for the Analysis of Codon Usage and Sequence Composition". Bioinformatics for DNA Sequence Analysis. Methods in Molecular Biology. Vol. 537. pp. 207–232. doi:10.1007/978-1-59745-251-9_10. ISBN 978-1-58829-910-9. PMC 2953947. PMID 19378146.

External links

• DNA codon chart organized in a wheel