Hi. I have posted on many places, they should not be
doing standard DNA preps and the experiment we need
to see is to see a caesium chloride density gradient
ultracentrifugation (not a gel)... If indeed the DNA
has arsenic, it should be getting denser and we would
see that as a band shift. Ethidium bromide's mode of
action would not be affected by arsenic substition.
As chemDroid wrote, there is no reason to believe that arsenic would have any impact on this process.
With a claim this important, we cannot do enough to try to disprove it. Only after we try everything we know and get consistently convincing evidence that arsenic is indeed incorporated into the DNA can we start believing it.
The bigger problem is that if it turns out the result is bogus this will be a net negative, both for NASA and for the scientific community, the public at large will not see this as proof that 'the system works' but as proof that they were being duped.
It has gotten to the point with NASA that when they make a life-based announcement, the Bayesian-style rational response is to ignore them entirely. It isn't too big a step from here to think that this research ought to be simply shut down, so that it can get out of the funding stream and then at least there's a chance the funding will go somewhere useful.
From the way they handled the whole thing from the start with the "aliens, but living here" spin to finding out the results aren't all that solid, it seems they need to clean some house.
Restructuring NASA is a hard problem maybe even impossible. But I do think it's still producing good enough stuff that removing it would be a mistake. I'm a believer in public research. It has produce some incredible benefits to society in the 20th century and hopefully will continue in the 21st.
If that is the case, then assuming there is arsenic in the DNA: how did they manage to PCR it? I would expect it to wreck havoc with the polymerase.
I would expect the radius and pitch not be drastically influenced. However, three dimensional structural prediction is quite difficult and it feels a bit uncomfortable speculating.
At any rate, you'd have to extract and crystallize a fragment of DNA that was particularly enriched for As, which would necessitate most of the other controls that people are suggesting anyway. You'd probably have a pretty good confirmation/refutation of the paper's claims by the time you were set up to shoot x-rays at a crystal.
I would guess that it doesn't since amplifying the sequence was successful.
Anyway, if the calculations and assertions made in the blog (and the commenters) turn out to be correct, this will be a big black eye for Science (the journal...) for publishing this.