56.7%GC3 content

54.5Effective codons (Nc)

248Coding sequences

12/26GC3 rank here

Scope: nuclear genes only

NCBI table 1 (Standard). Do not apply these frequencies to mitochondrial genes, where AGA, AGG, ATA and TGA carry different meanings. The four reassignments.

What distinguishes this table

The most constrained choice in Polar bear is glutamine: of its 2 synonymous codons, CAG takes 75% of the family. Phenylalanine sits at the other end, spread almost evenly across its options (evenness 1.00 against 0.81 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 Dog (r = 0.994) and least with M. tuberculosis (r = 0.791). 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, Polar bear leans hardest on TAC (+0.039 against the mean) and avoids TAT most (-0.039). Those two are the codons that most distinguish this table from the others.

Preferred and avoided codons

Amino acid	Preferred	Freq	RSCU	Avoided	Freq	RSCU
Alanine A	GCC	0.385	1.54	GCG	0.142	0.57
Arginine R	CGG	0.218	1.31	CGT	0.077	0.46
Asparagine N	AAC	0.531	1.06	AAT	0.469	0.94
Aspartate D	GAC	0.532	1.06	GAT	0.468	0.94
Cysteine C	TGC	0.532	1.06	TGT	0.468	0.94
Glutamate E	GAG	0.556	1.11	GAA	0.444	0.89
Glutamine Q	CAG	0.749	1.50	CAA	0.251	0.50
Glycine G	GGC	0.334	1.34	GGT	0.159	0.63
Histidine H	CAC	0.591	1.18	CAT	0.409	0.82
Isoleucine I	ATC	0.450	1.35	ATA	0.188	0.56
Leucine L	CTG	0.403	2.42	CTA	0.066	0.39
Lysine K	AAG	0.550	1.10	AAA	0.450	0.90
Phenylalanine F	TTC	0.509	1.02	TTT	0.491	0.98
Proline P	CCC	0.326	1.30	CCG	0.145	0.58
Serine S	AGC	0.246	1.47	TCG	0.062	0.37
Threonine T	ACC	0.338	1.35	ACG	0.150	0.60
Tyrosine Y	TAC	0.595	1.19	TAT	0.405	0.81
Valine V	GTG	0.462	1.85	GTA	0.119	0.47

Full codon usage table

Amino acid	Codon	Frequency	RSCU
Alanine A	GCC	0.3848	1.539
	GCT	0.2487	0.995
	GCA	0.2243	0.897
	GCG	0.1422	0.569
Arginine R	CGG	0.2182	1.309
	AGA	0.2178	1.307
	AGG	0.2098	1.259
	CGC	0.1719	1.031
	CGA	0.1050	0.630
	CGT	0.0773	0.464
Asparagine N	AAC	0.5310	1.062
Asparagine N	AAT	0.4690	0.938
Aspartate D	GAC	0.5324	1.065
Aspartate D	GAT	0.4676	0.935
Cysteine C	TGC	0.5323	1.065
Cysteine C	TGT	0.4677	0.935
Glutamate E	GAG	0.5562	1.112
Glutamate E	GAA	0.4438	0.888
Glutamine Q	CAG	0.7489	1.498
Glutamine Q	CAA	0.2511	0.502
Glycine G	GGC	0.3339	1.336
	GGA	0.2575	1.030
	GGG	0.2499	1.000
	GGT	0.1587	0.635
Histidine H	CAC	0.5910	1.182
Histidine H	CAT	0.4090	0.818
Isoleucine I	ATC	0.4502	1.351
	ATT	0.3618	1.085
	ATA	0.1880	0.564
Leucine L	CTG	0.4034	2.420
	CTC	0.1838	1.103
	CTT	0.1354	0.812
	TTG	0.1306	0.784
	TTA	0.0813	0.488
	CTA	0.0656	0.394
Lysine K	AAG	0.5501	1.100
Lysine K	AAA	0.4499	0.900
Methionine M	ATG	1.0000	1.000
Phenylalanine F	TTC	0.5086	1.017
Phenylalanine F	TTT	0.4914	0.983
Proline P	CCC	0.3256	1.302
	CCT	0.2690	1.076
	CCA	0.2603	1.041
	CCG	0.1451	0.580
Serine S	AGC	0.2456	1.474
	TCC	0.2134	1.280
	TCT	0.1922	1.153
	AGT	0.1488	0.893
	TCA	0.1381	0.829
	TCG	0.0619	0.371
Threonine T	ACC	0.3383	1.353
	ACA	0.2637	1.055
	ACT	0.2477	0.991
	ACG	0.1503	0.601
Tryptophan W	TGG	1.0000	1.000
Tyrosine Y	TAC	0.5949	1.190
Tyrosine Y	TAT	0.4051	0.810
Valine V	GTG	0.4618	1.847
	GTC	0.2397	0.959
	GTT	0.1799	0.720
	GTA	0.1186	0.474

Provenance

Computed from 248 RefSeq coding sequences for Ursus maritimus, 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.

Use this table

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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