Who would have suspected that a hand-held genetic test used to unmask sushi bars pawning off tilapia for tuna could deliver deep insights into evolution, including how new species emerge? And who would have thought to trawl through 5 million of these gene snapshots – called "DNA barcodes" – collected from 100,000 animal species by hundreds of researchers around the world and deposited in the U.S. government-run GenBank database?
Animals have two kinds of DNA.
In humans, there are 3 billion of these pairs, grouped into about 20,000 genes.
Mitochondria contain 37 genes, and one of them, known as COI, is used to do DNA barcoding.
Unlike the genes in nuclear DNA, which can differ greatly from species to species, all animals have the same set of mitochondrial DNA, providing a common basis for comparison.
Around 2002, Canadian molecular biologist Paul Hebert – who coined the term "DNA barcode" – figured out a way to identify species by analysing the COI gene.
On the one hand, the COI gene sequence is similar across all animals, which makes it easy to pick out and compare.
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