About 10,000 years ago, the teosinte plant underwent a mutation that would change the world. The tough greenish husks surrounding its golden grains disappeared, and the plant began its long evolution into what we now call corn.
It’s a story that’s well-known in the scientific community, but researchers at the University of Wisconsin-Madison only recently discovered where that mutation occurred: a single letter in the plant’s long string of DNA.
DNA looks like a twisted ladder, and each rung of the ladder is made up of four types of molecules called nucleotides. They are represented by the letters G, A, T and C, and they code how living things look and function.
The finding, published in the journal Genetics, shows just how complex the molecular makeup of life can be, and how a single molecule among millions just like it can change the course of history.
“There were lots of mutations (in corn),” said John Doebley, an author of the study and a professor at UW-Madison. “But this was the big one.”
The scientists were able to identify the single gene responsible for the major change essentially by reenacting the mutation. They mapped out the genomes of generations of teosinte plants and set up molecular markers in the data — sort of like highway signposts — to point out clues to which gene controls what physical trait. Eventually they found the exact DNA nucleotide that, when changed, resulted in the husk disappearing.
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