COI (Cytochrome C Oxidase Subunit I)
Definition
The 648 bp mitochondrial gene region proposed by Paul Hebert in 2003 as the universal barcode locus. Its combination of interspecific variation and intraspecific conservation makes it suitable for identifying most animal species from a small sequence read.
- Proposed by
- Paul Hebert, 2003
- Length
- Approximately 648 bp
- Role
- Universal animal barcode locus
- Forensic use
- Individual and species identification alongside STR profiling
Common questions
How does COI barcoding complement STR profiling in a forensic case?+
STR profiling individualises within a known species, typically human, while COI barcoding first establishes which species a biological sample came from, which matters in wildlife crime or when a stain of unknown origin needs species confirmation before any individualisation is attempted.
Is a 648 bp COI barcode enough to distinguish every animal species?+
No, it works well for most groups but a small number of closely related or recently diverged species show too little COI divergence to separate reliably, so those cases need a supplementary marker or a different gene region entirely.
Related terms
- BOLD Systems
- Barcode of Life Data System (University of Guelph, Canada). Holds over 9 million COI reference barcodes linked to voucher specimens, with mandatory...
- DNA Barcode
- A short, standardised sequence from a defined locus used to identify a specimen to species by comparison against a curated reference library....
- ElePhant Database
- A curated STR reference database for African savanna and forest elephants and Asian elephants, used to assign ivory to individual animals or...
- Minibarcode
- A 100-200 bp sub-region of the COI locus amplified when DNA is too degraded for the full 648 bp amplicon. Shorter target...
- STR (Short Tandem Repeat)
- A genomic locus where a 2, 7 base-pair unit is repeated in tandem a variable number of times between individuals. The variation...