Calculate codon usage bias metrics — RSCU, GC3 content, and effective number of codons (ENC) — for any coding sequence. Use this tool when optimizing a gene for heterologous expression: highly expressed host genes typically use a preferred subset of codons, and matching your gene’s codon usage to the host’s tRNA pool can dramatically improve protein yield. Low ENC values (approaching 20) indicate strong bias toward a subset of codons, while values near 61 suggest relatively uniform usage across synonymous codons.

Metrics

• RSCU (Relative Synonymous Codon Usage): Ratio of observed to expected frequency
• GC3 Content: GC content at the third codon position
• ENC (Effective Number of Codons): Measures codon usage bias (20 = extreme bias, 61 = no bias)