From Scientific American:
Genetic material once dismissed as mere “junk” may in fact be responsible to the evolution of simple invertebrates into more complex organisms sporting backbones, according to a new study. Tiny snippets of the genome known as microRNA were long thought to be genomic refuse because they were transcribed from so-called “junk DNA,” sections of the genome that do not carry information for making proteins responsible for various cellular functions. Evidence has been building since 1993, however, that microRNA is anything but genetic bric-a-brac. Quite the contrary, scientists say that it actually plays a crucial role in switching protein-coding genes on or off and regulating the amount of protein those genes produce.
(Picture: The lamprey, the jawless fish that represents one of the earliest vertebrates, has several more microRNAs than the proto-vertebrate sea squirt).
Now, researchers from Dartmouth College in Hanover, N.H., and the University of Bristol in England report in Proceedings of the National Academy of Sciences USA that these tiny genetic segments could be responsible for the evolution of animals with backbones, noting that they found a surfeit of microRNA in the genomes of the earliest vertebrates, such as lampreys (jawless fish), when compared with invertebrates like sea squirts.
More here.
