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>> Me
>>the backbone is not important, it's a break in the rungs of the DNA ladder
>>that's important because that's where all the digital information is stored.
>Robert J. Bradbury <bradbury@www.aeiveos.com>
>John, this simply isn't true.
I'll grant you that "not important" was a bit of an exaggeration, after all, with just a small change in the helix geometry of DNA and guanine will be able to bind with thymine and thus produce a mutation. However the sugar phosphate backbone is pretty robust, on the other hand the purine and pyrimidines that make up the rungs are only held together by weak hydrogen bonds, only about 5% as strong as a standard covalent bond. Besides a direct mechanism radiation might also increase the concentration of rare (one part in 10^5) tautomeric forms of the 4 bases allowing for example Cytosine to pair up with Adenine instead of Guanine as it should.
The rungs are where the action is, even severe damage to the backbone could theoretically be repaired, but destroy enough of the rungs and the information is simply gone, even Nanotechnology couldn't bring it back. Just change GAG to GTG at a specific point in the part of the DNA helix that codes for the Beta chain in hemoglobin and you have sickle cell anemia.
John K Clark jonkc@att.net
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