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It would be nice to be able to immediately identify life forms with a handheld device, without having to collect samples and submit them for analysis. Unfortunately, given the current state of scientific knowledge and technical know-how, a species-identification device similar to a Star Trek Tricorder will not be available anytime soon.
Taxonomy refers to the classification and naming of groups of living things according to shared characteristics. Traditionally, scientists have identified species using the rules of Linnaean taxonomy, which classifies species according to their shared characteristics and differences. But a Canadian scientist has developed an alternative and complementary approach, called DNA Barcoding.
Did you know? Currently there is a worldwide shortage of qualified taxonomists. Even if a new species is identified with a unique DNA barcode, it still must be classified by a taxonomist.Paul Hebert of the University of Guelph first proposed DNA Barcoding in 2003. It differs fundamentally from the Linnaean method of classification, which is based on phenotypic characteristics–an organism’s visible traits. By contrast, DNA barcoding is an approach to taxonomy based on genotypic characteristics–an organism’s genetic material.
DNA barcoding classifies each species using a short stretch of nucleotides (molecules that form the building blocks of DNA) obtained from the gene cytochrome c oxidase 1 (CO1). Roughly 400-800 base pairs (guanine-cytosine and adenine-thymine) in length, this gene, or short sequence, is found in mitochondrial deoxyribonucleic acid (DNA found in the mitochondria). This particular gene was chosen because its nucleotide sequence varies considerably between each animal species, making it a very effective tool for identifying birds, mammals, fish, amphibians, reptiles, and insects.
Best Friends Forever - Taxonomy and Barcoding
Called “barcodes,” because DNA sequencing produces images that look similar to the barcodes found on items in a supermarket, these short sequences of DNA can identify individual species. However, a barcoding sequence alone cannot describe or classify a previously unidentified species. In other words, DNA barcoding complements traditional taxonomy rather than replacing it. DNA barcoding can determine whether a species has been previously identified, but it cannot label an entirely new one. When a new species is discovered with a unique DNA barcode, a taxonomist must still properly classify it in relation to other known species.
Did you know? Cytochrome c oxidase 1 (CO1), has proven to be a highly efficient tool for identifying many kinds of animals. Unfortunately, it is not an effective gene for identifying plants.DNA barcoding provides a method that is reliable, rapid, economical, and accurate. Once they are derived through DNA sequencing, barcodes can be put into a digital databank, making the information readily accessible online to scientists and researchers the world over! It may not be a Tricorder, but it still sounds futuristic, doesn't it?
Five key components are necessary to create a system for DNA barcoding. First, specimens or samples (tissue cultures, genetic material, etc.) need to be collected. Samples may be whole specimens, body parts, or even tiny tissue samples. Second, a molecular laboratory must amplify (or multiply) small amounts of DNA, through a process called PCR (Polymerase Chain Reaction), to ensure there is enough DNA for DNA sequencing (Sanger Sequencing). Today, most of these labs have automated DNA sequencing machines that can provide an exact record of the sequence of nucleotides within the CO1 gene. Third, a computational method (or algorithm) is used to sort the resulting DNA barcoding sequences in order to differentiate specimens of previously unidentified specimens from species that have already been identified. Next, an identification tag–-usually a numerical identifier--is assigned to the organism. Finally, the information is added to a powerful database.
The International Barcode of Life (iBOL) is a multinational task force that has been set up to manage the largest database of species barcodes in the world: the Barcode of Life Database, or BOLD. Twenty-six different nations have invested in the project and assumed various responsibilities. For the database to be properly maintained, researchers must be equipped to handle the vast amount of data that is entered into the system.
So far, roughly 157,000 species have been assigned barcodes. That's roughly equivalent to the number of people needed to fill two large football stadiums. Go barcoding!
Barcoding at the Toronto Zoo (CurioCity Video)
http://www.explorecuriocity.org/Community/ActionProjects/Zoo.aspx Biodiversity Institute of Ontario (University of Guelph)
http://www.biodiversity.uoguelph.ca/ iBOL (International Barcode of Life)
http://ibol.org/about-us/what-is-ibol/ BOLD Systems
Holmes, B. 2004. Barcode me. New Scientist, 182:32-35. Lim, BK. 2009. Barcoding life: Magazine of the Royal Ontario Museum Magazine of the Royal Ontario Museum. ROM. 4:24-31.