The gene comes from fir trees, found throughout North America and commonly used as Christmas trees. The trees produce a chemical that can be used in perfume in place of ambergris—but with a catch.

　　“There's a problem that many people wouldn't consider. In the tree, the chemical is mixed with many others. That makes separation a challenge,” Bohlmann says.”It's like trying to isolate sugar from a biscuit.”

　　This is where science becomes useful. When Bohlmann learned that fir trees produce the ambergris-like chemical, he decided to use his gene know-how to find the instructions for how to make the ambergris-substitute.

　　Bohlmann found that gene and took it out of the tree cells. Then he did something that might sound strange to someone who doesn't work in genetics: Bohlmann put the gene from the tree into yeast(酵母) cells.

　　Yeast may sound familiar because it's used to make things like bread, wine and beer. Biologists like to work tith yeast because it easily adopts new genes and changes its features and behavior. When Bohlmann put the fir tree into the yeast, the yeast started making the same chemical that had seen produced by the tree.

　　Perfumers pay big money for ambergris because it is a fixative, which means it holds a smell in place on a person's body.

　　“Cheap perfumes smell good in the first hour or so and then everything it gone.” explains Bohlmann. “But expensive perfumes are much more stable. Their smell lasts much longer, for hours or even a day after you apply them.”

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