Phascolarctos cinereus
Synonymous codon usage in Koala (Phascolarctos cinereus), computed from 250 RefSeq coding sequences. Third positions are 53.8% G or C, below the median across the 26 organisms catalogued on this site, making it 14th of 26 by that measure. An effective number of codons of 55.2 indicates weak bias: the closer that value sits to 61, the more evenly an organism spreads its synonymous choices.
NCBI table 1 (Standard). Do not apply these frequencies to mitochondrial genes, where AGA, AGG, ATA and TGA carry different meanings. The four reassignments.
The most constrained choice in Koala is glutamine: of its 2 synonymous codons, CAG takes 73% of the family. Asparagine sits at the other end, spread almost evenly across its options (evenness 1.00 against 0.84 for glutamine). Those two families are where a codon-optimizer has the most and the least room to move.
Measured across all 59 sense codons, this table correlates most closely with Horse (r = 0.997) and least with M. tuberculosis (r = 0.734). A sequence tuned for the first would need little adjustment to move here; one tuned for the second would need a great deal.
Relative to the average across the 26 organisms on this site, Koala leans hardest on TGT (+0.064 against the mean) and avoids TGC most (-0.064). Those two are the codons that most distinguish this table from the others.
| Amino acid | Preferred | Freq | RSCU | Avoided | Freq | RSCU |
|---|---|---|---|---|---|---|
| Alanine A | GCC | 0.381 | 1.52 | GCG | 0.085 | 0.34 |
| Arginine R | AGA | 0.227 | 1.36 | CGT | 0.082 | 0.49 |
| Asparagine N | AAT | 0.501 | 1.00 | AAC | 0.499 | 1.00 |
| Aspartate D | GAT | 0.502 | 1.00 | GAC | 0.498 | 1.00 |
| Cysteine C | TGT | 0.524 | 1.05 | TGC | 0.476 | 0.95 |
| Glutamate E | GAG | 0.544 | 1.09 | GAA | 0.456 | 0.91 |
| Glutamine Q | CAG | 0.728 | 1.46 | CAA | 0.272 | 0.54 |
| Glycine G | GGC | 0.330 | 1.32 | GGT | 0.148 | 0.59 |
| Histidine H | CAC | 0.542 | 1.08 | CAT | 0.458 | 0.92 |
| Isoleucine I | ATC | 0.456 | 1.37 | ATA | 0.180 | 0.54 |
| Leucine L | CTG | 0.345 | 2.07 | CTA | 0.077 | 0.46 |
| Lysine K | AAG | 0.520 | 1.04 | AAA | 0.480 | 0.96 |
| Phenylalanine F | TTC | 0.511 | 1.02 | TTT | 0.489 | 0.98 |
| Proline P | CCT | 0.308 | 1.23 | CCG | 0.119 | 0.48 |
| Serine S | AGC | 0.228 | 1.37 | TCG | 0.049 | 0.29 |
| Threonine T | ACC | 0.358 | 1.43 | ACG | 0.118 | 0.47 |
| Tyrosine Y | TAC | 0.547 | 1.09 | TAT | 0.453 | 0.91 |
| Valine V | GTG | 0.437 | 1.75 | GTA | 0.135 | 0.54 |
| Amino acid | Codon | Frequency | RSCU | Share of family |
|---|---|---|---|---|
| Alanine A | GCC | 0.3808 | 1.523 | |
| GCT | 0.3084 | 1.234 | ||
| GCA | 0.2258 | 0.903 | ||
| GCG | 0.0850 | 0.340 | ||
| Arginine R | AGA | 0.2274 | 1.364 | |
| AGG | 0.2261 | 1.357 | ||
| CGG | 0.1928 | 1.157 | ||
| CGC | 0.1426 | 0.856 | ||
| CGA | 0.1291 | 0.775 | ||
| CGT | 0.0819 | 0.491 | ||
| Asparagine N | AAT | 0.5012 | 1.002 | |
| AAC | 0.4988 | 0.998 | ||
| Aspartate D | GAT | 0.5017 | 1.003 | |
| GAC | 0.4983 | 0.997 | ||
| Cysteine C | TGT | 0.5239 | 1.048 | |
| TGC | 0.4761 | 0.952 | ||
| Glutamate E | GAG | 0.5443 | 1.089 | |
| GAA | 0.4557 | 0.911 | ||
| Glutamine Q | CAG | 0.7277 | 1.455 | |
| CAA | 0.2723 | 0.545 | ||
| Glycine G | GGC | 0.3295 | 1.318 | |
| GGA | 0.2653 | 1.061 | ||
| GGG | 0.2571 | 1.028 | ||
| GGT | 0.1481 | 0.592 | ||
| Histidine H | CAC | 0.5417 | 1.083 | |
| CAT | 0.4583 | 0.917 | ||
| Isoleucine I | ATC | 0.4560 | 1.368 | |
| ATT | 0.3638 | 1.091 | ||
| ATA | 0.1802 | 0.541 | ||
| Leucine L | CTG | 0.3452 | 2.071 | |
| CTC | 0.1878 | 1.127 | ||
| TTG | 0.1540 | 0.924 | ||
| CTT | 0.1417 | 0.850 | ||
| TTA | 0.0940 | 0.564 | ||
| CTA | 0.0773 | 0.464 | ||
| Lysine K | AAG | 0.5199 | 1.040 | |
| AAA | 0.4801 | 0.960 | ||
| Methionine M | ATG | 1.0000 | 1.000 | |
| Phenylalanine F | TTC | 0.5111 | 1.022 | |
| TTT | 0.4889 | 0.978 | ||
| Proline P | CCT | 0.3077 | 1.231 | |
| CCC | 0.2992 | 1.197 | ||
| CCA | 0.2735 | 1.094 | ||
| CCG | 0.1195 | 0.478 | ||
| Serine S | AGC | 0.2279 | 1.367 | |
| TCC | 0.2176 | 1.306 | ||
| TCT | 0.1978 | 1.187 | ||
| AGT | 0.1566 | 0.940 | ||
| TCA | 0.1515 | 0.909 | ||
| TCG | 0.0486 | 0.292 | ||
| Threonine T | ACC | 0.3580 | 1.432 | |
| ACA | 0.2736 | 1.094 | ||
| ACT | 0.2502 | 1.001 | ||
| ACG | 0.1182 | 0.473 | ||
| Tryptophan W | TGG | 1.0000 | 1.000 | |
| Tyrosine Y | TAC | 0.5474 | 1.095 | |
| TAT | 0.4526 | 0.905 | ||
| Valine V | GTG | 0.4373 | 1.749 | |
| GTC | 0.2364 | 0.946 | ||
| GTT | 0.1912 | 0.765 | ||
| GTA | 0.1351 | 0.540 |
Computed from 250 RefSeq coding sequences for Phascolarctos cinereus, sampled and counted codon by codon. Frequencies are relative within each amino acid family. Page generated 2026-08-09.
The full derivation of GC3, RSCU and the effective number of codons, along with the limits of each, is set out once in the methods note rather than repeated on every page.
Nucleora codon-optimizes a coding sequence against this table directly, then folds the result and reports where structure would interfere with expression.
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