Genbank vs Fasta: Which Format Preserves Plasmid Features

A plasmid file format is the container that stores DNA sequence plus, in some formats, features such as CDS, promoters, primers, and notes. FASTA generally keeps letters. GenBank-style files keep letters and a feature table. Proprietary map formats may keep layout and enzyme metadata that other tools cannot read.

This comparison is for labs that need annotations to survive backups, CRO handoff, and software changes.

What You Are Trying to Preserve

A cloning map is not only the sequence. It is the intended translation, the primer binding sites, the spacer, the remaining Type IIS sites, and comments about a scar that looks like a real codon. If those objects die on export, the next person will re-annotate from memory and will get a codon wrong.

FASTA Is a Sequence Receipt, Not a Map

Use FASTA when the receiver only needs bases: an oligo pool order that wants a raw insert, or a search tool that rejects feature files. Do not use FASTA as the lab's only copy of a 7-kb expression plasmid. The His tag, the secret stop, and the extra ATG from a primer will not be marked.

If you must send FASTA, send a second document that lists feature coordinates against that exact sequence. Two files that can drift are worse than one GenBank file, but better than FASTA alone.

GenBank-Style Files Are the Portable Annotation Layer

A .gb or .gbk file can carry CDS features with translation qualifiers, promoters, primers, and notes. Most molecular biology programs can import some dialect of this family. Dialects differ: a qualifier one tool writes may be ignored by another. After import, check that translations still start at the same ATG.

For archive and CRO handoff, export GenBank from the current map and open it in a second tool before you call the export successful. Circular topology flags are a frequent miss; a circular plasmid imported as linear will look "wrong" at the origin wrap-around.

Sequence software should be evaluated on round-trip fidelity: export, import, and still see primers and CDS. Zettalab's molecular tools are one workspace to evaluate for that round trip inside a project, not a claim that every vendor qualifier will survive.

Proprietary Files and Why You Still Need an Open Export

Vendor-specific map files (for example, some desktop .dna map formats) can store enzyme lists, numbering, and pretty layout. They are fine as working files. They are a risk as the only archival copy if the license lapses or a partner does not own the same software.

Keep the working file for daily editing. Keep a dated GenBank export for the freezer equivalent of the map. Put both IDs in the experiment record when a plasmid lot is released.

A Practical Archive Rule

When a construct is declared in use, store: native working file, GenBank export, FASTA of the full molecule for tools that need it, and a human-readable feature list if the construct is legally or clinically sensitive. Name them with the same construct version.

When switching software, import the GenBank, not a screenshot PDF. Re-run translation. Re-mark primers if they dropped. Only then design the next oligo.

FAQ

Which plasmid file format preserves annotations?

Annotated text formats in the GenBank family are the usual portable choice because they store feature locations and qualifiers with the sequence. FASTA does not. Proprietary map formats often preserve even more UI metadata but may not open elsewhere. For lab survival, keep a GenBank-style export even if you work daily in a vendor file. After every export, reopen the file and confirm CDS translations and primer features are still present.

Is FASTA ever enough for plasmid handoff?

It is enough when the receiver will not edit features: a synthesis vendor that wants an insert, or a search index. It is not enough when the receiver must clone, express, or review a fusion. If legal or quality staff need to know where a tag sits, send annotated files. Adding a color-coded PDF does not replace coordinates; PDFs are pictures. Pictures do not BLAST and they do not translate.

What breaks during GenBank round trips?

Custom qualifiers, primer direction, topology (circular versus linear), and translation tables are common losses. Some tools split one CDS into gene plus CDS and another tool collapses them. Always translate after import. If a His tag vanished as a feature but the bases are still there, the sequence survived and the annotation did not; that is still a failed handoff for a cloning lab.

How should we archive plasmids before changing software?

Freeze a version, export GenBank and FASTA, keep the native file, and open the GenBank in the destination tool while you still have the old license. Repair features immediately. Do not wait until the next cloning crisis. Store the pair of files in the project next to the ELN record that released the DNA lot. A sequence file workflow is a reasonable place to document which export button the lab standardizes on.

Do plasmid libraries on the web replace local annotated files?

Public or vendor libraries, including a searchable plasmid library, are starting points. Once you modify a cassette, the working copy is your molecule and must be saved with your features. Citing "we used the library backbone" without a versioned export is how two labs diverge while using the same nickname. Copy to the project, annotate the change, and archive that file.

Conclusion

Use FASTA for sequence-only jobs. Use GenBank-style files as the portable annotation layer. Treat proprietary maps as working files that still need an open export. Check translations after every import. Connected map tools such as Zettalab's molecular biology workspace are useful when the archive file and the notebook lot ID live in one project. Export the annotated plasmid the day you declare the clone real, not the day the old software license expires.