Genetics: DNA barcoding

Rose Eveleth

Imagine this: you’re walking through the jungle of Costa Rica and you see a butterfly on the ground that you don’t recognize. It’s dead, and you take a tiny bit of its wing and pop it into a little machine that sequences the DNA and tells you exactly the species of butterfly you’re holding.

Ok, so maybe we’re not quite there yet, but DNA barcoding – the term used for quickly identifying species through a single genetic marker, is a booming area of research (as well as source of controversy).  The idea is that we identify a single marker, for example a segment of a specific gene that is common to all life.  So far, the best candidate has been the CO1 gene, which is found in mitochondrial cells of all known animals and plants.  Mitochondrial DNA (including the CO1 gene) is passed on to offspring only from the mother, and has an extremely high mutation rate compared to nuclear DNA.  This makes the CO1 sequence even of extremely close relatives measurably different.

Paul Herbert, father of DNA barcoding thinks that in ten years we’ll have a portable machine that can take a piece of organic matter, sequence the CO1 gene and determine the species for us.  The implications of this are huge, as are the applications.

Already DNA has unlocked a huge portion of the biological world.  Recently, DNA barcoding has lead to the discovery of new species.  Many see a bevy of practical uses.  In July, Dirk Steinke of the Canadian Centre for DNA Barcoding published a paper on the technology’s applications to the ornamental fish trade.

Steinke and his lab used the CO1 gene to sequence 391 species from 8 different coral reefs and found that 98% of the species could be determined via barcoding technology (the species exhibited “barcode clusters,” segments of the CO1 gene unique to that species only).  What this means is that even species that look similar, can be identified via their barcode (much like different types of apples at the store).   Similar studies have been done with butterflies and birds that show the CO1 gene to be highly effective as a barcode unit.

Critics suggest that the DNA barcoding is not nearly as universal as has been claimed.  A 2003 paper out of Berkeley by Will Kipling and Daniel Rubinoff points out that the proponents of DNA barcoding might be getting ahead of themselves.  Kipling and others are worried that with barcoding technology there will be a dismissal of morphologists: men and women who can identify species based on a complex set of physical characterizes.  These researchers have often spent years working on identifying and describing their groups of species, and Kipling believes that this complex and well developed knowledge is both more consistent and more effective than relying on a single gene.

Paul Herbert’s enthusiasm has never waned.  The CBOL has already catalogued over 25,000 species.  Soon “researchers will find a barcode linked to just about anything encountered anywhere on the planet,” Herbert says.

The team at Berkeley does not deny the usefulness of barcoding technology as a tool for biologists and geneticists alike to define and discover new species.  Kipling simply isn’t ready to buy into many of the purported uses of the technology such as on the spot identification. This hasn’t stopped many from trying.  The Consortium for the Barcode of Life (CBOL) has several good images and explanations of the process, as does the International Barcode of Life (iBOL) – why they don’t work together I have no idea.

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