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DNA barcodes make their mark


Consortium for the Barcode of Life
  Color-coded genetic sequences serve as "DNA barcodes" for a hermit thrush (far left), an American robin, a bumblebee and a honeybee. The gray bars stand for genetic differences.

DNA fingerprinting isn't just for humans anymore: The "barcodes of life" are being read in other species as well, and they're being used to crack down on smugglers, track down disease carriers and trace the effects of climate change.

About 350 experts from 50 countries will be meeting in Mexico over the next week to discuss the rising number of applications for the technology. One of the major items on the agenda is to seal a global deal to extend the DNA barcode system to plants.

That could help genetic sleuths to get a better handle on where timber is being harvested illegally, where herbal medicines really come from, and where plant diseases are being spread.

"Biodiversity scientists are using DNA technology to unravel mysteries, much like detectives use it to solve crimes," David Schindel, executive secretary of the Consortium for the Barcode of Life, said in a news release previewing the weeklong Mexico City meeting. "It is having a profound impact on our understanding of organisms in nature and how they interact with the environment."

The international consortium and the Instituto Biologia at the Universidad Nacional Autonoma de Mexico are co-hosts of the meeting at the Mexican Academy of Sciences. Researchers will be sharing the success stories they've accumulated over the past six years.

DNA barcoding really got its start in 2003, when scientists agreed on a standard for fingerprinting a species' genetic code.

Anyone who's watched any modern-day cop show knows that DNA can serve to match a crime-scene sample with a suspect (or rule that suspect out as the perpetrator). But is there a quick, reliable way to determine from a DNA sample whether it came from a rare parrot or a common chicken?

The consortium's scientists settled on a 645-base-pair region of mitochondrial genetic code, known as the COI or COX1 gene, to serve as the standard fingerprint for a species. That region mutates quickly enough that you can tell the difference between closely related species, but slowly enough that individuals within a species have similar barcodes.

Here are just some of the applications cited by the consortium:

  • In 2003, a Brazilian man was caught trying to smuggle 58 eggs through an airport. The man said they were quail eggs, but police suspected they were rare (and regulated) parrot eggs. Although the eggs never hatched, DNA barcoding revealed that the embryos of blue-bellied or yellow-faced Amazon parrots were inside 51 of the eggs, macaws were inside three others, and yellow-crowned parrots were inside the last four. That justified an arrest.
  • Researchers recently reported in the journal Conservation Genetics that they sequenced the barcode region for 25 mammals and reptiles from Africa and South America that commonly turn up in international trade. Many of the species, such as Old World monkeys and Nile crocodiles, are not supposed to be harvested. The researchers hope the barcodes will help counter the rising trade in bushmeat, a market that was estimated last year to be worth as much as $15 billion.
  • Officials at the Federal Drug Administration say DNA barcoding can reliably distinguish the seedpods of star anise (Illicium verum), an herb commonly used in teas, cooking and herbal remedies, from the otherwise identical seedpods of a sister species (Illicium anisatin) that is considered a health risk due to the presence of neurotoxins.
  • The International Barcode of Life Project, headquartered in Canada, is presenting a study showing that eight bat species feed on more than 300 types of insects - making up one of the largest food webs ever discovered. Such research can show "how diets may be changing due to climate change," said the Smithsonian Institution's Scott Miller, chair of the Consortium for the Barcode of Life.
  • London's Natural History Museum has partnered with an educational charity to get 1,000 students involved in "Project BarkCode," aimed at collecting genetic samples from 10,000 trees in Britain starting next year.
  • In Canada, students collected fish samples from stores nationwide for DNA analysis, and found a significant level of seafood mislabeling. In the United States, the FDA hopes to use DNA barcoding to cut down on mislabeling and other illegal and hazardous practices.

Eventually, scientists aim to develop a database of 5 million samples from 500,000 species. The project will almost certainly have public health benefits: Even now, researchers are collecting barcodes for disease-spreading mosquitoes in India, black flies that transmit river blindness disease in South America, and parasites that afflict frogs and livestock in Mexico and Central America.

DNA fingerprinting could contribute to an early warning system for the spread of disease, or help inspectors track down the source of food contamination. "This is an example of where new genetic technology can be transformative to society," George Amato, director of the Sackler Institute for Comparative Genomics at the American Museum of Natural History, said in a recent report on barcoding.

For more examples of barcoding at work, check out this clickthrough gallery that highlights how DNA analysis can help document global biodiversity.

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