DNA barcoding is a technique for characterizing species of organisms using a short DNA sequence from a standard and agreed-upon position in the genome. DNA barcode sequences are very short relative to the entire genome and they can be obtained reasonably quickly and cheaply. The cytochrome c oxidase subunit 1 mitochondrial region (COI) is emerging as the standard barcode region for higher animals. It is 648 nucleotide base pairs long in most groups, a very short sequence relative to 3 billion base pairs in the human genome, for example.
The ‘barcode’ metaphor is useful though not correct in fine detail. That is, all the products of one type on a supermarket shelf (like a 2-litre bottle of Coca-Cola) share exactly the same 11-digit barcode, which is distinct from all other barcodes. DNA barcodes vary among individuals of the same species, but only to a very minor degree. If the DNA barcode region is effective, the minor variation within species will be much smaller than the differences among species.
Learn more about DNA barcoding in two CBOL brochures:
Barcoding projects have four components:
- The Specimens: Natural history museums, herbaria, zoos, aquaria, frozen tissue collections, seed banks, type culture collections and other repositories of biological materials are treasure troves of identified specimens.
- The Laboratory Analysis: Barcoding protocols [pdf, 561Kb] can be followed to obtain DNA barcode sequences from these specimens. The best equipped molecular biology labs can produce a DNA barcode sequence in a few hours for as little as $5 per specimen. The data are then placed in a database for subsequent analysis.
- The Database: One of the most important components of the Barcode Initiative is the construction of a public reference library of species identifiers which could be used to assign unknown specimens to known species.
There are currently two main barcode databases that fill this role:
- The Data Analysis: Specimens are identified by finding the closest matching reference record in the database. CBOL has convened a Data Analysis Working Group to improve the ways that DNA barcode data can be analyzed, displayed, and used.