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This Single Mutation That Makes Corn—Corn!

July 30, 2015
Corn has been a fundamental base crop for 10,000 years and we depend on it for fuel, food and a multitude of other products. I cannot even fathom what society would be like without it. To think that maize diverged from its ancestral teosinte due to a single genetic change base change (A, T, G, or C in its DNA), a single nucleotide polymorphism (SNP), just highlights how lucky we are to have a crop that can give so much to the world. The Washington Post recently published a great piece on the history of corn and how it has transformed to the food that know it as today:

‘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. 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.”

Mutations, genetic changes, are the source of all differences seen in DNA. Since DNA codes for RNA, which then code for proteins, a single genetic change on a nucleotide could result in new protein tasks which could ultimately affect outward characteristics like eye color or kernel size. Most single mutations rarely affect outward characteristics, so it is extremely rare that one SNP could produce such a drastic change.

According to Researchers for Evidence, the origin of Naked Kernels was caused by a single amino acid substitution in tga1.

Our results document how morphological evolution can be driven by a simple nucleotide change that alters protein function.”

The SNP that causes the difference between maize and teosinte relies in the gene tga1, which regulates transcription (DNA à RNA) responsible for the coding of proteins which are responsible for the architecture of corn that can create the naked kernels in corn vs. the enclosed kernels in teosinte.

“This finding 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.”

Many people fear genetic modification, but as you can see, evolution is always modifying the genetic makeup of all living things anyway—just at a much slower pace.