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Evolution of vertebrates earliest link discovered in 'junk DNA'

By Paul Wallis     Feb 12, 2008 in Science
British researchers have discovered what they think is the key to the evolution of vertebrates, “micro RNA”. These are recently discovered small molecules, found in what is ever more ridiculously still being called “junk DNA.”
Researchers at Dartmouth College and Bristol University have put together a picture of gene structures which they trace from primitive organisms to humans. The micro RNA is very diverse, abundant in vertebrates, and rare in invertebrates.
The micro RNA is used in gene expression. It’s how a gene operates.
Gene expression is defined by as:
The translation of information encoded in a gene into protein or RNA. Expressed genes include genes that are transcribed into messenger RNA (mRNA) and then translated into protein, as well as genes that are transcribed into types of RNA such as transfer RNA (tRNA) and ribosomal RNA (rRNA) that are not translated into protein. Gene expression is a highly specific process in which a gene is switched on at a certain time and "speaks out"."
This is a missing link of an important kind, because it shows a huge split in the animal kingdom’s genes.
The almost complete absence of the necessary RNA from invertebrates also shows that vertebrates are a major evolutionary departure from their invertebrate ancestors.
Dartmouth College News tells the story of its finds:
"There was an explosive increase in the number of new microRNAs added to the genome of vertebrates and this is unparalleled in evolutionary history," says Heimberg.
The team studied the genomics of primitive living fishes, such as sharks and lampreys, and their spineless relatives, like the sea squirt. By reconstructing the acquisition history of microRNAs shared between human and mice, the researchers determined that the highest rate of microRNA innovation in the vertebrate lineage occurred before the divergence between the living jawless fishes like the lamprey and the jawed fishes like the shark, but after the divergence of vertebrates from their invertebrate chordate relatives, such as the sea squirt
That period was one of Earth’s biological golden ages, a huge diversity of life which filled the ancient oceans.
Most of the genes are “also required for organs unique to vertebrates, like the liver, pancreas, and brain”, according to one of the co authors of the study.
Don’t know about the brain. Insects have brains, but they must be based on a different genome, different DNA and RNA, and obviously a different biology.
Another point about this discovery is that it has some obvious medical applications. If you’re trying to grow a new leg, brain, pancreas, or liver, you need to know how these genes work, and you definitely need to know how genes are expressed.
Theoretically, it’s possible to replace anything, if you know how to operate the genes.
Most of the fundamental discoveries of science have been a result of pulling things apart and learning how they’re put together.
I just hope that the term “junk DNA” will wind up on the scrapheap, where it and the mentality that came up with that expression (pun intended) belongs. That idea could have meant this discovery might never have been made.
Nature doesn’t make junk.
More about Genes, Vertebrates, Micro rna
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