Investigations in New York’s Chinatown are a regular occurrence, but Sergios-Orestis Kolokotronis’ mission was purely scientific. The professor of genetics at Barnard College sent his students out to trawl the markets’ open-air displays of exotic fish, fruit and vegetables, and purchase anything being sold as crocodile meat. When they brought the meat back and analysed it, they found it wasn’t from crocodile at all. Its origins weren’t exactly clear, but for all the world it looked suspiciously like some kind of python.
Slice it and package it in the right way, and one reptile’s meat looks – and may even taste – like another. From mislabeled crocodile to fake fur, a global industry has thrived for centuries by supplying shops and markets with fraudulent or counterfeit products. Until now, perhaps. Scientists and authorities think they can finally put an end to this unscrupulous trading by using a technique that can identify species from its genetic material like a barcode on a cereal box.
To see how authorities are beginning to use this method to tackle fraud, you need to travel just over 10 miles from Chinatown’s markets to a large, square, greyish building in Newark, New Jersey. There, on the fifth floor, one lab is trying to catch everything from fraudulent fish, to mislabeled toy cats, to illegally prepared sheep placenta in traditional Chinese medicine. The lab is run by the United States Customs and Border Protection, but the science in question – DNA barcoding – is becoming more and more useful for law enforcement and research around the world.
To demonstrate, Matthew Birck, the lead barcoding scientist at the Newark lab, walks to a large white freezer and pulls out a black garbage bag. Inside is a very frozen, very intact fish – head to tail. Towards the back of the fish popsicle, Birck had cut a small square for sequencing a little bit of DNA called the CO1 gene – also known as the “barcode of life”.
Normally Birck and his lab don’t get an entire fish – or an entire anything really. Instead, they often get parts of the animal in the form of pills, snippets of hair, and chunks of vegetables or meat. Most recently they’ve been inundated with fish filets, which are nearly impossible to identify. “There’s nobody who can look at a fish fillet and tell you what it is,” Birck says. And importers will go to great lengths to cut and dye their fillets to look like the fish they’re trying to imitate.
But for Birck, as long as there’s DNA to extract, no amount of cutting and dying can pass tilapia off as salmon. He extracts a sample of DNA, copies the gene they’re looking for and sequences it. They then compare the sequence they have with a database of animals and plants. If it matches something in the database, they’ve got an answer. So if a fillet says it’s salmon, Birck can compare that DNA with the salmon barcode. “This is really cut and dried,” he says, “it matches or it does not, end of story.”
The principle behind DNA barcoding is that you amplify and analyse a small snippet of a gene that differs slightly but in a detectable way from species to species. The idea isn’t terribly new: the decision to use the CO1 gene as the “barcode” was made around 2003, mainly due to work by Paul Herbert at the University of Guelph in Ontario, Canada.