COI (Cytochrome C Oxidase I)
Definition
A mitochondrial gene encoding subunit I of the respiratory enzyme cytochrome c oxidase. Its intermediate evolutionary rate makes it the primary barcode marker for animals; the standard forensic amplicon spans approximately 658 base pairs.
- Type
- Mitochondrial gene
- Function
- Subunit I of respiratory enzyme cytochrome c oxidase
- Standard amplicon
- Approximately 658 bp
- Forensic use
- Primary barcode marker for forensically important insects
Common questions
Why is COI used specifically to identify insects in a forensic entomology case?+
Insect species found on a body can only be aged and interpreted correctly for a post-mortem interval estimate once the species is confirmed, and larvae and eggs often lack the morphological features adults have, so a short mitochondrial DNA barcode gives a reliable identification when visual keys cannot.
What makes COI's evolutionary rate suitable for species-level identification?+
It mutates fast enough that closely related species accumulate distinguishing differences, but slowly enough that individuals of the same species remain nearly identical at the barcode region, giving a workable gap between within-species and between-species variation.
Related terms
- BOLD
- Barcode of Life Data System, an international curated database linking COI sequences to verified voucher specimens with collection locality and taxonomic annotation....
- 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...
- DNA Barcoding
- Species identification using a short, standardised region of the mitochondrial genome. For animals, the primary barcode marker is a 648-base-pair segment of...
- Morphological Identification
- Species determination based on external or internal physical features. Reliable and cheap for adults and many late-instar larvae, but fails on early...
- Species Complex
- A group of closely related species that are nearly identical in morphology but behaviourally or ecologically distinct. Molecular methods are often the...