Part of an organism’s DNA base sequence that serves to identify which species the organism belongs to. The sequence selected for barcoding should ideally show marked variation between species but minimal variation within species. In many animal groups the internationally agreed standard sequence is a 648bp region of the mitochondrial gene for cytochrome oxidase subunit 1 (CO1), whereas in plants the chloroplast genes matK and rbcL are used instead. The barcode is generated by amplifying a specimen of DNA using specially designed primers with the polymerase chain reaction, and then sequenced. The base sequence is converted into a graphic image of different coloured lines representing the four constituent bases, similar to a barcode on an item in a supermarket. The Barcode of Life Datasystems (BOLD) has compiled a database containing barcodes for nearly 280 000 plant, animal, and fungal species (as of early 2018). An investigator can search the database to find a match with a reference barcode and thus identify which species they are dealing with.

http://www.ibol.org/ Website of the International Barcode of Life project