Newly evolved gene may have changed humans’ brains


The completion of human and primate genome sequences (including some closeextinct relatives) reveals a great deal about the evolutionary innovations behind modern humans. All indications are a large collection of relatively subtle genetic changes added up to considerable differences in our brains and anatomy.

So, it was a bit shocking to see a headline claiming a single gene separated us from our fellow apes. The article behind the headline turned out to be wrong, of course. But there was an additional research paper behind that article. The story this told turned out to be rather interesting, even after the hype was stripped away.

The second paper was the product of a research group studying the evolution of human micro RNAs. These are short pieces of RNA that form a “hairpin” structure: two stretches of complementary sequence that can base pair to form a double helix, separated by a short loop that lets the RNA fold back on itself.

Micro RNAs, unlike messenger RNAs, don’t code for other proteins. Instead, they help control which messenger RNAs do get made into proteins. The hairpin structure is recognized by a complex of proteins inside the cell, which process it in a way that leaves a short guide sequence exposed. The guide sequence can then base pair with sequences on messenger RNAs, leading the protein complex to them. The complex will typically either block the messenger RNA from being translated into protein or cause it to be destroyed altogether.

The net result of this: a single micro RNA can determine whether a much larger number of genes are made into proteins. In that sense, they act a lot like the proteins that bind to DNA and regulate the activity of large collections of genes.

Written By: John Timmer
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