endogenous retroviruses!!!!
So this is really cool.
There's the DNA of thousands (millions?) of viruses spliced into your DNA! Every cell (almost) in your body has the mark of millions and millions of generations of viral infections permanently etched into your genetic code.
When viruses attack, they splice their own instructions into the DNA of the host cell. If that cell is an egg cell, and that egg cell comes to term, the mutation can remain in the DNA of the offspring. That mutation survives as part of the new DNA of the organism, and all its descendents.
Scientists have isolated the DNA of over 98,000 viruses in the Human genome, and over 150,000 fragments of these viruses.
And one of the coolest things about this is it represents a seperate line of evidence for common ancestry. If a virus inserted its genetic code into a common ancestor of humans and chimps, that virus code is still there, in the same place in both the human and the chimp genome. The genes of humans and chimps have shifted around on the chromosomes, but the virus code most of the time is found in the analogous place in both.
Looking at our DNA, we can trace back our common ancestry with other animals living today. Scientists can chart the endogenous retroviruses in various creatures DNA, and use the similarities and differences to chart a taxonomic tree, and see how it compares to the trees built based on anatomy, genetic similarity, etc. It's a line of evidence that points to no possible conclusion other than common ancestry.
But even more interesting to me, it points to a mechanism by which evolution can be accelerated when a species is under stress.
I'll post more about that soon.
Read Carl Zimmer's story about this in the meanwhile on his blog:
http://loom.corante.com/archives/2006/03/13/the_sixtymillionyear_virus.php#comments
posted by Siamang @ 9:15 PM
3 comments
3 Comments:
I'm waiting for an ID supporter to say that these viruses are how the "designer" nudges evolution along.
I mean, the viruses ARE gene-splicing themselves into our genome.
I'm not a scientist.... standard disclaimer.
But that's not my understanding. My understanding is that it's anywhere in our DNA. Junk and non-junk.
Where its inserted into junk DNA it can obviously still cause a frame shift in the gene sequence of genes that normally get expressed.
But the advantage of the viruses that are inserted into junk dna is that natural selection doesn't weed them out. So they become markers.
I don't think they're tough to trace, given that they ride along in analogous locations among all creatures which have that common ancestor. You can tell if a sequence of genes is there or not, as long as it's more than a couple of digits. We do know the normal single bit mutation rate, and so we can with a good deal of certainty date the rate of evolutionary change. This also can tell us, by looking at the junk dna of a chimp and a human, roughly how long ago the split was.
If they've become part of the expressed (non junk)DNA of the organism, then natural selection would weed out significant errors as well.
All of these are part of the genome of the organism. Once they are, there is no mechanism I know of that would cause the code from retroviruses to be treated any differently by the organism from the rest of the genome.
This is just how I assume it works. Don't take any of this as science.
Read the Zimmer article on the original post.
Also, for more info on some of this stuff, read this PZ Meyers article here:
http://pharyngula.org/index/weblog/comments/cats_candy_and_evolution/P25/
Thanks for the compliment, TX.
As far as the negative responses, check the IIDB thread here:
http://www.iidb.org/vbb/showthread.php?t=159951
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