Codon Usage in Seqqio: Counts, Synonymous Fractions, and GC3
Profile codons in DNA or RNA with explicit frame and genetic-code settings, reproduce a tested synthetic example, and avoid overinterpreting descriptive counts.
The method is recorded as Seqqio-CodonUsage-v1. Its main advantage is explicit bookkeeping: DNA or RNA alphabet, NCBI genetic code, reading frame, skipped leading bases, terminal remainder, record-level results, and a pooled batch profile remain visible. That makes the table suitable for review without turning frequency into a biological claim.
Set molecule, code, and frame
Open Codon Usage and choose Single sequence or FASTA batch. Select DNA or RNA before pasting the sequence: DNA accepts T and RNA accepts U. Choose the NCBI genetic code and Frame 1, 2, or 3. Seqqio accepts only concrete bases for this analysis; ambiguity and gaps are rejected rather than distributed probabilistically.
| Frame | Leading bases excluded | What is counted |
|---|---|---|
| 1 | 0 | Complete triplets beginning at base 1 |
| 2 | 1 | Complete triplets beginning at base 2 |
| 3 | 2 | Complete triplets beginning at base 3 |
After the selected offset, one or two terminal bases can remain. Seqqio reports that remainder and excludes it from every codon and GC-position denominator. Alternative start codons retain their ordinary amino-acid assignment in this descriptive table; the first codon is not automatically forced to methionine.
Reproduce the built-in codon profile
Load synthetic_cds_1, keep DNA, NCBI Code 1, and Frame 1, then select Analyze codon usage. The Seqqio engine processed 903 bases as 301 complete codons with zero trailing bases. Coding GC was 53.378%; GC1 was 54.817%, GC2 was 53.821%, and GC3 was 51.495%.
The eight most frequent codons in that executed control were GCA: 11; CCT: 10; TTC: 9; CGG: 8; TAT: 8; TCT: 8; TGG: 8; and AAG: 7. These counts describe one intentionally synthetic record. They are not a host reference, a preferred-codon table, or evidence for expression in any organism.
Read the three frequency views correctly
| Field | Calculation | Use |
|---|---|---|
| Count | Occurrences of that exact codon | Auditable raw evidence |
| Per 1,000 | 1,000 x codon count / all complete codons | Compare records with different total codon counts |
| Synonymous fraction | Codon count / counts for codons assigned to the same amino acid or stop under the selected code | Inspect within-group choice |
The EMBOSS cusp documentation describes the same core reporting pattern: observed count, frequency per 1,000, and proportion within a redundant codon set. Seqqio adds explicit DNA/RNA, frame, genetic-code, batch, and GC-position receipts. The NCBI genetic-code tables remain the source for deciding which codons belong to each amino-acid group.
Understand pooled FASTA results
In FASTA batch mode, each record gets its own profile and the aggregate counts sum successful records. Pooled percentages and fractions are recalculated from the pooled counts. They are not an unweighted average of record percentages, which would give a short sequence the same influence as a long sequence. Failed records remain visible but do not contribute counts.
Save the pooled long-form TSV when you need one 64-row profile and the per-record TSV when record identity matters. The Biopython CodonTable API is an independent reference for NCBI table assignments and was used in Seqqio's validation. A frequency table alone still cannot identify the organism, measure translation efficiency, or recommend a synthesis design.
When codon usage analysis is a good fit
Use this workflow to describe a CDS set, compare GC-position patterns, teach synonymous groups, or produce a traceable input for a later analysis. If the goal is to redesign DNA, first define the host reference and constraints. The Seqqio Reverse Translation guide explains how explicit codon weights can drive a separate deterministic or degenerate output without claiming multi-objective optimization.
Codon Usage is part of Seqqio's 39-application Windows 64-bit workspace. See the Seqqio workspace overview for the common local history, batch, and export model. The toolkit is offered as a US$99 one-time purchase with no activation key.
References
- National Center for Biotechnology Information. The Genetic Codes NCBI Taxonomy genetic-code reference Authoritative codon-to-amino-acid assignments for supported translation tables.
- EMBOSS contributors. cusp manual EMBOSS application documentation Independent documentation for codon counts, per-1,000 frequency, and redundant-set proportions.
- Biopython contributors. Bio.Data.CodonTable module Official Biopython API documentation Independent programmatic representation of NCBI codon tables used during validation.