COI (COX1)
Definition
Cytochrome-c oxidase subunit I gene. The 658-base-pair Folmer fragment is the globally adopted barcode-of-life marker for animals, curated in BOLD Systems and used for CITES casework species identification.
- Full name
- Cytochrome-c oxidase subunit I
- Barcode fragment
- 658 bp Folmer fragment
- Database
- BOLD Systems
- Application
- CITES casework animal species identification
Common questions
Why was the Folmer fragment of COI chosen as the universal animal barcode?+
It amplifies reliably across a very broad range of animal taxa with universal primers, and it carries enough interspecific sequence variation to separate species while remaining conserved enough within a species to be diagnostic, which made it practical to standardise globally rather than choosing a different marker per taxon.
How is COI barcoding applied in a CITES wildlife trafficking case?+
A short sequence from seized material, such as meat, hide, or scale, is amplified and compared against reference sequences in BOLD Systems to identify the species and determine whether it is a CITES-listed protected species, supporting a wildlife trafficking charge.
Related terms
- 16S rRNA
- The small-subunit ribosomal RNA gene in bacteria (~1,550 bp). The V3-V4 hypervariable region (~470 bp) is amplified with universal bacterial primers for...
- BOLD Systems
- Barcode of Life Data System (University of Guelph, Canada). Holds over 9 million COI reference barcodes linked to voucher specimens, with mandatory...
- Cytochrome B (Cyt B)
- A mitochondrial protein-coding gene widely used in forensic species identification before COI barcoding was standardised. Still used because its reference database for...
- ITS Region
- Internal transcribed spacer region, flanking the 5.8S rRNA gene between the 18S and 28S subunits in fungi and plants. The ITS1-5.8S-ITS2 fragment...
- PCR-RFLP
- PCR followed by restriction fragment length polymorphism analysis. A restriction enzyme cuts the amplicon at species-specific recognition sites; the resulting fragment pattern...
- SILVA
- Curated ribosomal RNA sequence database (Max Planck Institute for Marine Microbiology, Bremen). Provides quality-filtered 16S, 18S, 23S, and 28S reference alignments for...