Vertebrate mitochondrial code
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The vertebrate mitochondrial code (translation table 2) is the genetic code found in the mitochondria of all vertebrata.
Evolution
[edit | edit source]AGA and AGG were thought to have become mitochondrial stop codons early in vertebrate evolution.[1] However, at least in humans it has now been shown that AGA and AGG sequences are not recognized as termination codons. A -1 mitoribosome frameshift occurs at the AGA and AGG codons predicted to terminate the CO1 and ND6 open reading frames (ORFs), and consequently both ORFs terminate in the standard UAG codon.[2]
Incomplete stop codons
[edit | edit source]Mitochondrial genes in some vertebrates (including humans) have incomplete stop codons ending in U or UA, which become complete termination codons (UAA) upon subsequent polyadenylation.[3][4][5][6]
Translation table
[edit | edit source]| Amino acids biochemical properties | nonpolar | polar | basic | acidic | Termination: stop codon |
| 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 | UGA | (Trp/W) Tryptophan | A | ||
| UUG | UCG | UAG | UGG | 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 | (Met/M) Methionine | ACA | AAA | (Lys/K) Lysine | AGA | Stop | A | ||
| AUG[A] | 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 | |||||
- A The codon AUG both codes for methionine and serves as an initiation site: the first AUG in an mRNA's coding region is where translation into protein begins.[7]
Differences from the standard code
[edit | edit source]| DNA codons | RNA codons | This code (2) | Standard code (1) | |
|---|---|---|---|---|
AGA |
AGA |
STOP = Ter (*) |
Arg (R)
| |
AGG |
AGG |
STOP = Ter (*) |
Arg (R)
| |
ATA |
AUA |
Met (M) |
Ile (I)
| |
TGA |
UGA |
Trp (W) |
STOP = Ter (*)
|
Alternative initiation codons
[edit | edit source]See also
[edit | edit source]References
[edit | edit source]- This article contains public domain text from the NCBI page compiled by Andrzej Elzanowski and Jim Ostell.[9]
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- ^ The Genetic Codes