How to Find Open Reading Frames in Seqqio: Six Frames, Genetic Codes, and Start Rules
Search complete open reading frames on direct and reverse strands, interpret coordinates and overlapping starts, and avoid treating an ORF as a gene call.
The method identifier is Seqqio-OrfFinder-v1. The tool can search one record or a FASTA batch, but every record is processed independently and every coordinate remains local to its source sequence.
Choose a genetic code before interpreting starts and stops
Open ORF Finder, select the genetic code, then decide which frames and strand to search. Frames 1, 2, and 3 correspond to offsets 0, 1, and 2 in the searched 5-prime-to-3-prime sequence. To cover six reading frames, run all three frames on Direct and then all three on Reverse.
| Control | Available choice | Interpretation |
|---|---|---|
| Code | Supported NCBI genetic code | Defines initiators, stops, and internal translation |
| Frames | All, 1, 2, or 3 | Limits offsets searched on the selected strand |
| Strand | Direct or Reverse | Chooses one biological orientation per run |
| Starts | ATG only or NCBI initiators | Restricts which exact codons can open an ORF |
| Minimum aa | Positive whole number; default 30 | Filters translated length, excluding the terminal stop |
ATG only is the stricter policy. NCBI initiators also accepts exact codons marked as starts in the selected table. The NCBI genetic-code reference shows why a codon can translate one way internally yet act as an initiator in the first position. Ambiguous codons never initiate an ORF in Seqqio.
Use the built-in CDS as a controlled first run
Click Load example to insert the first synthetic complete CDS, or the full synthetic CDS set in batch mode. Keep Code 1, Frames All, Strand Direct, Starts ATG only, and Minimum aa 30 for the first run. Click Search sequence or Search FASTA batch. The examples are deterministic application controls and are explicitly not organism references.
Each result reports frame, strand, one-based inclusive start and end, amino-acid length, protein, and nucleotide sequence. The nucleotide output is written 5-prime to 3-prime on the reported strand and includes the terminal stop codon. The protein begins with M under initiation rules and omits the terminal stop symbol.
| Result type | Displayed coordinate rule |
|---|---|
| Direct strand | Start is less than or equal to end |
| Reverse strand | Start is greater than or equal to end, following biological orientation |
| Nucleotide sequence | Includes start and terminal stop, written in the reported strand's 5-prime-to-3-prime direction |
| Protein sequence | Initiator is M; terminal stop is excluded |
Interpret overlapping starts deliberately
Seqqio returns an ORF for every eligible start. If several starts occur before the same in-frame stop, the reported ORFs can overlap and share that stop. This is an explicit Seqqio rule. Do not assume that the longest result replaces every nested result, and do not expect exact parity with a tool that suppresses some nested starts.
The implementation was compared with the standalone NCBI ORFfinder 0.4.3 for shared cases, including direct and reverse standard-code ORFs and a table-11 alternative GTG initiator. The official NCBI ORFfinder is also a useful external comparison. Seqqio's every-start rule remains a documented difference rather than a claim of identical output.
A complete ORF is not automatically a gene
The 30-amino-acid default is a reporting filter, not a confidence threshold. Shorter values are supported. ORF Finder does not infer transcription, expression, exon structure, ribosome use, evolutionary conservation, or biological function. A complete start-to-stop interval is sequence evidence that satisfies the selected rules; gene annotation requires additional evidence.
A result can also disappear for a clear methodological reason: the region lacks a terminal in-frame stop, the start is in another frame or strand, the chosen table assigns codons differently, or the ORF is shorter than the current minimum. Adjust one control at a time and record the settings with the export.
When ORF Finder is a good fit
Use ORF Finder to inspect candidate coding intervals, teach frame and strand logic, compare start policies, or create traceable nucleotide/protein pairs from local sequences. Use a dedicated annotation pipeline when you need genomic gene models, comparative evidence, or transcript-aware inference.
ORF Finder is part of the 39-application Seqqio workspace for Windows 64-bit. The Seqqio overview explains the common record, batch, history, and export model. The toolkit is a US$99 one-time purchase with no activation key.
References
- National Center for Biotechnology Information. ORFfinder NCBI web application Official ORFfinder interface and documentation for genetic code, start mode, strand, length, and nested-ORF controls.
- National Center for Biotechnology Information. The Genetic Codes NCBI Taxonomy genetic-code reference Authoritative translation-table assignments and initiator definitions used to interpret start and stop behavior.