There's a funny similarity to our DNA ...
Borna Virus Discovered in Human Genome - Carl Zimmer - NYTimes.comIn the physican universe dark matter is only about 70% of all matter, but in humans "dark DNA" is 97%+ of all DNA. So our DNA is about 2% protein coding, 8% retrovirus, and 90% other - including non-retroviral virus origin and "structural". (Yes, I know that's "four times" and Zimer says "seven times" - his numbers are more likely correct.)
...Fossil viruses are also illuminating human evolution. Scientists estimate that 8.3 percent of the human genome can be traced back to retrovirus infections. To put that in perspective, that’s seven times more DNA than is found in all the 20,000 protein-coding genes in the human genome.
So from a DNA perspective, are we basically an ambulatory viral ecosystem with a fraction of information capacity that does things like make brains and bodies? Seems a bit much, but it turns out even some of the most important protein coding DNA is of viral origin. In a companion post on his blog Zimmer writes ...
... a virus protein called syncitin ... is essential for placentas to develop. Cells push the protein to their surface, where it lets them latch onto other cells, fusing together to create a special layer through which nutrients can pass from mother to child. The protein got its start on viruses, which use it to latch onto host cells and fuse to them, allowing their genes to slip in.But recent research has revealed an intriguing new twist to our viral legacy. It turns out that the viral surface protein in question has a second job. It also tamps down the immune system of its host...
So is there any non-structural DNA in humans that's not of fundamentally viral origin?
See also: Presser on the bornavirus article ... UTA News Center
PS. A search on Preeclampsia and bornavirus has 180 hits today, but I think they appear to be loose and coincidental relationships. I didn't see research relating bornavirus-like superinfection triggering auto-immune placental disruption and thus pre-eclampsia / toxemia.
Update 1/30/2010: io9 quotes Frank Kelly: "[T]he human genome has evolved as a holobiontic union of vertebrate and virus... ". A Coral holobiont is "the entire community of living organisms that make up a healthy coral head".
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