AUDIE CORNISH, HOST:
You, me and baker's yeast. We all have something in common - a common ancestry. NPR's Nell Greenfieldboyce reports on a new study that shows us how much.
NELL GREENFIELDBOYCE, BYLINE: On the surface, yeast and humans look pretty different. Humans look like, well, you. Meanwhile, if you rip open a package of yeast, you'll see dry, brown granules. Biologist Edward Marcotte studies yeast at the University of Texas at Austin. He says on a lab dish yeast grows in colonies that look like little gooey white dots. And through a microscope...
EDWARD MARCOTTE: If you look down at an individual cell, it'll look kind of like a little ball. So if you imagine kind of a relatively smooth, slightly dimpled little golf ball, you'd have a pretty good idea for what a yeast cell would look like.
GREENFIELDBOYCE: He says that single cell, that microscopic golf ball, is your cousin.
MARCOTTE: Distant, distant cousin a billion years removed, but nonetheless, your cousin, which is an amazing thing.
GREENFIELDBOYCE: Marcotte says humans and yeast share thousands of similar genes, but he wondered, how similar are these genes really?
MARCOTTE: You know, we've been separated by a billion years of evolution. Do those genes really work the same way?
GREENFIELDBOYCE: He figured the best way to answer that question would be to try swapping them - disable a gene in yeast, replace it with the human version of that gene and then see if the yeast can survive. Scientists had done this already with some individual genes, but Marcotte wanted to test a lot more, about 500 key genes that yeast need for life.
MARCOTTE: And there's a postdoc in my laboratory named Aashiq Kachroo who was willing to tackle this slightly insane project.
GREENFIELDBOYCE: It was a brute force effort that took about three years. And here's the result...
MARCOTTE: Roughly half of them, we could replace the yeast genes with the human DNA, and the yeast were just fine.
GREENFIELDBOYCE: It turns out, for some jobs in the cell, it was like a billion years didn't matter. For example, the researchers looked at a whole bunch of genes involved in manufacturing cholesterol, which cells need to keep their shape. Marcotte says almost all of the human genes for that worked perfectly in yeast.
MARCOTTE: Humans and yeast are doing not only the same thing as each other, but the same thing that their last common ancestor a billion years ago was doing, and it's changed remarkably little over all of that time.
GREENFIELDBOYCE: A report on the study appears in the current issue of the journal Science. Nell Greenfieldboyce, NPR News.
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