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Let me unpack this, because the evolution of new genes is very cool. 1/n
Most of our genomes is not made of genes. A lot of it is “junk”—repetitive sequences with no function.
Sometimes mutations can cause these “non-coding” sequences to be transcribed by our cells, either into RNA, or all the way into proteins. 3/n
It’s not easy to reconstruct the origin of new genes from non-coding DNA, but sometimes the trail is still clear. 4/n
Christina Cheng of @Illinois_Alma and her colleagues have studied how fish in cold waters have evolved antifreeze genes from non-coding DNA. 5/n
@Illinois_Alma I first got to know Cheng when she and her colleagues were studying antifreeze in fish in Antarctica 20 years ago. Now they’re looking at fish in the Arctic Ocean too. 6/n
@Illinois_Alma By comparing the DNA of a group of related fish, Cheng and her colleagues could piece together the step by step process by which a piece of non-coding DNA became a gene with a function: keeping Arctic fish from freezing to death. 7/n
@Illinois_Alma Three different kinds of mutations helped create the new gene. First: duplication. Mutations can create extra copies of DNA. 8/n
@Illinois_Alma Mutation #2: Individual bases can change, too. Such changes can turn random sequences of DNA into instructions for a cell to start transcribing a stretch of DNA. 9/n
@Illinois_Alma Genes also need switches to turn them on at the right time and places. These switches get moved around the genome by parasitic pieces of DNA called mobile elements. 10/n
@Illinois_Alma So these three kinds of mutations turned a piece of DNA into a transcribed gene, encoded a structure of a molecule that helps blood keep from freezing, and ensured the gene was used only in the right place at the right time. Sweet! 11/11
@Illinois_Alma (PS, here’s the paper: pnas.org/content/116/10… )
