Sequence utilities / Codon usage
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Each row is a codon: count is the number of occurrences, per_thousand the frequency per thousand codons, and fraction its share among the synonymous codons for the same amino acid.
RSCU (relative synonymous codon usage) = observed count ÷ the mean count of its synonymous codons: 1 means no preference, above 1 preferred, and below 0.5 is usually regarded as rare.
Highly expressed genes (such as ribosomal proteins) usually show stronger bias than the genome as a whole; for heterologous expression, compare with the bias of the target host when optimising codons.
Enter CDS in the correct frame (starting at the start codon); sequences with internal stops or lengths not divisible by 3 are flagged. GC3 is the GC content at third codon positions.
RSCU: Sharp & Li 1986 (Nucleic Acids Res 14:7737); see also the codon adaptation index, Sharp & Li 1987 (Nucleic Acids Res 15:1281).
Counts are pooled over all sequences; up to roughly 50 MB is recommended in the browser.
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