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To identify Dr. McDonald had to perform a process called DNA sequencing on their samples. “Identifying species by their sequence barcode is almost exactly like going shopping. You pick out the items you want, some of them have price stickers on them, some of them don’t, and you take them to the cash register. As each item’s tag is scanned, the barcode on the item is the identifier: each item has a different barcode. When scanned, the exact item and that item’s price is displayed on the register’s screen as long as it’s in the database. With living organisms, each major group of organisms has a well-established “barcode” in animals we use a gene called co1, in plants we use a gene called rbcL, in fungi we use a gene called ITS, etc. A gene sequencer has the ability to read all of the letters of the genetic code between two primers, that act like target probes. They restrict the region you’re generating the sequence for, instead of getting the entire genome. Once the sequencer has given you all of the letters between your primers, you run that through the barcode database and it will tell you what species that barcode is from. It’s really nice because it can work on a very small piece of tissue, instead of relying on identification based on the entire, intact, organism.”


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