It is a gene that is often used as a DNA barcode to identify animal species. MT-CO1 gene sequence is suitable for this role because its mutation rate is often fast enough to distinguish closely related species and also because its sequence is conserved among conspecifics. Contrary to the primary objection raised by skeptics that MT-CO1 sequence differences are too small to be detected between closely related species, more than 2% sequence divergence is typically detected between such organisms,[11] suggesting that the barcode is effective. In most if not all seed plants, however, the rate of evolution of cox1 is very slow