Scientists have called it "junk DNA." They also refer these "junk DNA" as "selfish DNA" if they make no specific contribution to the reproductive success of the host organism. Selfish DNA replicates and passes from parent to offspring for the sole benefit of the DNA itself. However, researchers have discovered that DNA sequences from regions of what had been viewed as the "dispensable genome" are actually performing functions that are central for the organism. They concluded that the genes spur an almost acrobatic rearrangement of the entire genome that is necessary for the organism to grow.
It all happens very quickly. Genes called transposons in the single-celled pond-dwelling organism Oxytricha produce cell proteins known as transposases. The focus is on Oxytricha because it undergoes massive genome reorganization during development.
During development, the transposons appear to first influence hundreds of thousands of DNA pieces to regroup. Then, when no longer needed, the organism cleverly erases the transposases from its genetic material, paring its genome to a slim 5 percent of its original load.
The transposons actually perform a central role for the cell and they stitch together the genes in working form. To prove that the transposons have this reassembly function, scientists disabled several thousand of these genes in some Oxytricha. The organisms with the altered DNA failed to develop properly.
But the present study suggests that some selfish DNA transposons can instead confer an important role to their hosts, thereby establishing themselves as long-term residents of the genome.
References:
http://esciencenews.com/articles/2009/05/20/research.team
.finds.important.role.junk.dna
http://www.princeton.edu/main/news/archive/S24/28/32C04/
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