Find open reading frames in DNA and translate candidate coding regions instantly. This ORF Finder scans forward and reverse-complement frames, marks start and stop codons, ranks ORFs by length, and reports amino-acid sequences for cloning, annotation, and classroom genetics work.
Paste a DNA sequence and the tool updates every ORF result as you change reading-frame, start-codon, and minimum-length settings.
Start with a ready sequence, then paste your own FASTA or plain DNA sequence.
Paste a coding strand, genomic fragment, plasmid insert, or FASTA record. The tool keeps A, C, G, and T.
Length
56 nt
GC content
46.4%
Removed
0
Control which strand, start codons, and minimum protein length the scanner uses.
Live ORF result
Frame +1 spans bases 7 to 42 and starts with ATG.
ORFs
1
Top frame
+1
Complete
Yes
Coloured bars show detected ORFs. Red ticks mark stop codons in each frame.
Sort order starts with the longest ORF because longer uninterrupted coding frames usually deserve first review.
| Rank | Frame | Coordinates | Length | Start | Stop | GC% | Protein preview |
|---|---|---|---|---|---|---|---|
| 1 | +1 | 7–42 | 36 nt / 11 aa | ATG | TAA | 44.4% | MAELKRDGIAA |
This chart helps you compare candidate coding regions before you inspect the protein sequence.
An open reading frame is a DNA interval that can translate in one codon frame without meeting an internal stop codon. Many ORF workflows start at ATG and end at TAA, TAG, or TGA. That simple rule gives students and researchers a fast first pass through plasmid inserts, bacterial contigs, and coding-sequence fragments.
NCBI describes ORFfinder as a tool that searches a submitted DNA sequence, returns the range of each ORF, and gives the corresponding protein translation. Review NCBI ORFfinder. This calculator follows the same core idea for educational use, then adds visual frame maps and sortable candidate tables.
A long ORF does not automatically mean a real gene. Functional annotation also checks conserved domains, transcript evidence, ribosome-binding context, codon usage, and evolutionary conservation. For translation review after ORF detection, use the Codon Usage & Translation Tool to inspect codon counts and amino-acid properties.
The sequence input accepts FASTA text, copied plasmid sequence, or a plain DNA fragment. It strips headers, spaces, numbers, and punctuation so the scan uses only A, C, G, and T. The live length and GC cards help you spot incomplete pastes or unusually GC-rich inserts before you interpret ORFs.
The reading-frame selector controls strand logic. Use all six frames when you do not know the coding orientation. Use forward or reverse-only scanning after primer design, Sanger sequencing, or cloning maps identify direction.
The start-codon rule changes biological sensitivity. ATG-only mode matches most introductory genetics problems. Alternative-start mode includes GTG, TTG, and CTG, which can matter in bacterial annotation and synthetic biology screening.
The ORF map gives quick visual feedback. Long coloured bars indicate candidate coding regions, while red tick marks show stop codons. The result table then provides exact frame, coordinate, length, start codon, stop codon, GC percentage, and protein preview.
Enter a plain DNA sequence or FASTA text. The scanner keeps A, C, G, and T and removes spaces, numbers, and headers.
Scan all six reading frames when strand orientation is unknown, or limit the scan to forward or reverse frames when you know direction.
Use ATG only for standard classroom work, or include GTG, TTG, and CTG for bacterial alternative-start screening.
Compare ORF length, frame, start codon, stop codon, GC percentage, and translated amino-acid sequence.
DNA codons use triplets, so the same nucleotide string can produce three different forward-frame translations. The reverse complement adds three more possibilities. A real coding insert usually makes biological sense in one dominant frame, but sequencing reads and metagenomic contigs often arrive without orientation labels.
Translation starts with an initiation codon and stops at a termination codon. OpenStax explains how mRNA codons direct amino-acid addition during translation and how stop codons terminate the process. Read the OpenStax translation section.
| Frame | First codon starts at | Typical use | What to inspect |
|---|---|---|---|
| +1 | Base 1 | Known coding strand sequence | ATG context and stop position |
| +2 / +3 | Base 2 or base 3 | Frameshift comparison | Premature stop codons |
| −1 to −3 | Reverse complement | Unknown insert orientation | Long reverse-strand ORFs |
A student pastes a 63-base insert that contains ATG at base 7 and TAA at base 52. The ORF length equals 48 nucleotides, including the stop codon, and the translated protein contains 15 amino acids before termination. The +1 frame outranks the shorter alternatives, so it becomes the first coding candidate to inspect.
After that, the student can check target-region GC percentage with the GC Content Calculator before primer design.
A PCR amplicon may contain a coding region on either strand. Six-frame scanning can reveal a long ORF in frame −2 even when forward frames contain many stop codons. That pattern tells the user to inspect the reverse-complement sequence before ordering primers or planning expression.
When the sequence comes from an oligo or primer workflow, compare primer behaviour in the Oligo Analyzer after identifying the likely coding orientation.
Start with ORF detection, then translate the longest candidates. Next, compare codon usage, predicted protein length, GC percentage, and any known vector or primer constraints. This sequence of checks helps avoid a common mistake: choosing the longest ORF before confirming orientation and biological context.
Molecular workflows often connect ORF analysis with concentration and dilution planning. After you identify a coding insert, you may prepare primers with the Oligo Concentration Calculator or dilute working stocks with the Solution Dilution Calculator. Internal consistency across sequence analysis and wet-lab preparation reduces avoidable errors.
This tool finds candidate open reading frames, but it does not annotate promoters, ribosome-binding sites, introns, untranslated regions, signal peptides, or protein domains. Eukaryotic genomic DNA often needs transcript-aware analysis because splicing joins exons before translation. Viral and mitochondrial genomes may use genetic-code variations that this educational scanner does not model.
Use ORF length as a ranking signal. Then validate the candidate with translation, similarity search, expression evidence, and organism-specific annotation rules. The output supports education and research planning; it does not replace a curated genome annotation pipeline.
Use these tools after ORF detection to translate the coding sequence and evaluate sequence composition.