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Scientists at the University of Chicago studied a massive set of genetic variants of an ancient protein, discovering a myriad of other ways that evolution could have turned out and revealing a central role for chance in evolutionary history.
The study, published this week in Nature by University of Chicago graduate student Tyler Starr and his advisor Professor Joseph Thornton, is the first to subject reconstructed ancestral proteins to deep mutational scanning—a state-of-the-art technique for characterizing massive libraries of protein variants. The authors' strategy allowed them to compare the path that evolution actually took in the deep past to the millions of alternative routes that could have been taken, but were not.
Version - Protein - Function - Years - Function
Starting with a resurrected version of an ancient protein that evolved a new function some 500 million years ago - a function critical to human biology today—the researchers synthesized a massive library of genetic variants and used deep mutational scanning to analyze their functions. They found more than 800 different ways that the protein could have evolved to carry out the new function as well, or better than, the one that evolved historically.
The researchers showed that chance mutations early in the protein's history played a key role in determining which ones could occur later. As a result, the specific outcome of evolution depended critically on the way a serial chain of chance events unfolded.
History - Paths - Result - Evolution - Tyler
"By comparing what happened in history to all the other paths that could have produced the same result, we saw how idiosyncratic evolution is," said Tyler Starr, a graduate student in biochemistry and molecular biology at UChicago, who performed the paper's experiments. "People often assume that everything in biology is perfectly adapted for its function. We found that what evolved was just one possibility out of many that were just as good, or even better, functionally than...
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