Since the 1960s, scientists have researched
non-coding portions of DNA within human and animal genomes. These portions, commonly called "junk DNA," are sections of the DNA sequence that are not responsible for the construction of the proteins that compose a living animal. As a result, many researchers believed the non-coding segments were left-over genetic debris from millions of years of evolution. In the last decade, the "junk" has been found to be anything but, as scientists think it could play an important role in evolution, such as body shape.
Recently, researchers led by developmental biologist Moises Mallo of the Gulbenkian Institute of Science in Oeiras, Portugal have examined mutant mice bred by the institute that contain 24 pairs of ribs, compared to the 13 pairs in normal mice. This mutation was traced back to the deactivation of the
GDF11 junk gene, which controls another gene - OCT4 - that regulates stem cell development into many different cell types.
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| An x-ray of Moises Mallo's mice containing extra ribs. |
Snakes, which also have both genes, naturally have dozens of ribs along the length of their spine. Mallo and his team spliced non-coding sections of snake DNA into normal mouse embryos near the OCT4 gene to see if the snake GDF11 would cause a prolonged growth spurt in the embryo. The team found that the embryos grew large amounts of additional spinal cord, implying that the junk DNA does indeed play a role in body shape regulation of animals.
Developmental biologist Valerie Wilson of the University of Edinburgh commented on the junk DNA:
“There’s an immense amount of variation in body length across vertebrates, but within species the number of ribs and so forth stays almost exactly the same. There must be some ways to alter the expression of those [genes] regulating evolution to generate this massive amount of variation that we see across the vertebrates.”
Read more: http://www.sciencemag.org/news/2016/08/junk-dna-tells-mice-and-snakes-how-grow-backbone
It is so interesting to know that "junk DNA" actually plays an important role in the formation of species. I wonder what exactly our "junk DNA" codes for, since we already know what other DNA codes for.
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