Season 4, Episode 11: Bloodless
In this episode of ReGenesis, a child is mysteriously killed and his mother is the prime suspect. While the mother's description of the killer, a cryptic animal/monster (the river cat), is not convincing, the hair samples found in the nails of the dead body provides some biological material for testing. A relatively new molecular genetics approach, DNA barcoding, is used to solve the puzzle. DNA barcoding identifies the hair samples to be from an African cheetah (which will later be linked to an engineered animal). Barcoding leads to the release of an innocent suspect: in this case, the victim's mother.
Comparative DNA analysis and DNA barcoding
DNA and forensics have gone hand in hand for many years now. For example, comparisons of DNA evidence found at crime scenes to the DNA of suspects have helped to convict - or exonerate - countless individuals. But in this episode, we see DNA being used for a different kind of forensic investigation - namely, trying to figure out just what kind of animal killed Billy!
The information encoded in DNA molecules has been used in comparative studies of different organisms for several years. With the recent advancement of DNA sequencing technologies, many new applications of comparative DNA analysis have been introduced. One such technology - DNA barcoding - was pioneered in 2003 by Dr. Paul Hebert and colleagues at University of Guelph, Ontario. DNA barcoding is a species identification and discovery approach based on the analysis of short standardized genomic regions in mitochondria - that is, chunks of DNA that can identify a species just as a UPC barcode can identify a box of cereal or bottle of shampoo at the grocery store.
The standard DNA barcode for animal species is a 650 base long fragment of a mitochondrial gene-cytochrome c oxidase I (CO1, cox1). This fragment has been shown to provide species-specific resolution in more than 97% of the species in various taxonomic groups from mammals to insects. For example, if you compare the barcode region of a human to a chimpanzee, you will find about 9% sequence variation (or 60 diagnostic nucleotides). This level of variation between species, combined to a lack of variation within species, makes DNA barcoding a very robust species identification tool.
Around the world, taxonomic specialists are collaborating with molecular biologists and biodiversity scientists to develop DNA barcode "libraries" for many groups of organisms, from birds to fish to fungi. These barcode libraries are stored in a global web-accessible data base, the Barcode of Life Data system (BOLD), which can be used to identify a barcode sequence from an unknown specimen, as NorBAC does in this episode of ReGenesis. As of May 2008, BOLD contains about 390,000 DNA barcodes from 38,000 species. Scientists estimate that there are about 10 to 100 million species on Earth, so there is a lot more barcoding to be done!
So what?
In the next 5-10 years, scientists will have generated complete barcode libraries for many socio-economically important species of plants and animals, like those that are edible, useful, endangered, or even dangerous. In addition, DNA barcoding will significantly accelerate the rate of species discovery in all domains of life. Once the barcode libraries are established, barcode analysis can be performed directly from mixed environmental samples (such as water, soil or even air) by using next generation sequencing technologies such as parallel pyrosequencing.
And the holy grail of barcode analysis will be the development of a handheld DNA barcode reader, which will enable anyone at anytime to identify a biological specimen. While a device like this may sound fictional - like the Tricorder devices in Star Trek- the technologies needed to build it are available today!
DNA barcoding: something for everyone
DNA barcoding is the most powerful modern approach for species identification. As such, DNA barcoding can contribute in various fields from epidemiological studies to forensics where fast and accurate species identification is critical:
- DNA barcoding is used by food regulatory agencies to authenticate and validate the species used in food products; did you realize that a significant percentage of what we purchase as Red Snapper filet is, in fact, from a cheaper species of fish?!
- It is used by border control agents to identify invasive species that could damage the ecosystem(s) in the country into which they are being transported.
- It is used for rapid diagnosis of pathogens.
- It is used to identify the species of birds that strike airplanes, to help in determining flight patterns so that airline traffic can be routed around - rather than through - flight paths.
- And the list goes on…
Dr. Dan Janzen, a prominent tropical ecologist and conservation biologist, who has spent more than 40 years of his life in understanding and conserving biodiversity in tropical forests of Costa Rica, describes DNA barcoding as providing "something for everyone." He strongly believes that a handheld barcode reader will revolutionize species identification; so much so, that he compares it to such transformative technologies as the "printing press, Model T Ford, Kodak camera, cell phone, and Wright brother's airplane." Time will tell, but at the present pace at which the technology is developing, the wait might be a short one!
-- Mehrdad Hajibabaei, PhD
About the Author
Dr. Mehrdad Hajibabaei is the Associate Director of the Canadian Centre for DNA Barcoding (CCDB), Biodiversity Institute of Ontario, University of Guelph. He has a PhD in Biology (molecular evolution and bioinformatics) from the University of Ottawa. Dr. Hajibabaei joined Dr. Paul Hebert's lab at Guelph in September 2003, as the first postdoctoral fellow on DNA barcoding. During his postdoctoral research he pioneered the development of high throughput DNA barcoding and worked on DNA barcoding tropical Lepidoptera as well as barcode recovery from archival specimens. Dr. Hajibabaei is a founding member of the Canadian Centre for DNA Barcoding, where he continues his research on various aspects of DNA barcoding from theoretical aspects to technology development and data analysis. He has published numerous articles on DNA barcoding.
Want to read and learn more?
Check out the Canadian Centre for DNA Barcoding (CCDB) website at:
http://www.dnabarcoding.ca
To browse around the Barcode of Life Data System, go to:
http://www.barcodinglife.org
Learn more about the Consortium for the Barcode of Life (CBOL), an international initiative devoted to developing DNA barcoding as a global standard for the identification of biological species, at:
http://www.barcoding.si.edu
