Saturday, March 26, 2005

Whoa, where'd that gene come from ?

There's a paper in this week's edition of Nature magazine that talks about a surprising finding made by scientists at Purdue, namely that Arabidopsis, a plant, seems to be able to fix a defective gene that it shouldn't be able to fix. [Here's the link to the NYT article describing this, or, if you have a subscription, to the actual Nature paper] Basically, the information needed to fix the defective gene doesn't appear to be anywhere in the plant's DNA, yet the plant magically retrieves it from somewhere. The paper's author's speculate that the "missing" information is encoded in RNA [instead of DNA], and that there are RNA copies of the plant genome that act as a "cache" of genes that used to be around in earlier generations. When the plant is under stress and needs to fix a defective gene for which it doesn't have a working version in its DNA, it goes up to the attic [RNA], so to speak, blows the dust off some old genes that it "knows" used to work, and uses those to fix the broken gene. Certainly an interesting idea, we'll have to wait and see what else comes out of this line of inquiry.

My impressions, in no particular order:

- Score another one for RNA. In the last few years, it's become increasingly apparent that RNA isn't just a boring intermediate in the path from DNA to protein: small interfering RNAs [siRNAs], microRNAs and riboswitches are very active in regulating gene expression [microRNAs regulating up to a third of all human genes, by some estimates]; RNA molecules can act as enzymes to catalyze chemical reactions [a role normally reserved for proteins] and can be used instead of antibodies to bind tightly to specific proteins for therapeutic and experimental purposes etc. With the publication of this paper, there's now another putative role for RNA, namely that it acts as a "backup copy" of the genes of previous generations.

- I suspect this will provide fodder for the Intelligent Design folks, in the form of "Look, not even something as supposedly unassailable and 'simple' as the fact that DNA encodes our inherited information is really true ! How can the theory of evolution be accurate ?"

- It makes me wonder how many decades it will be before we can be sure that we really understand the genome, its maintenance, expression and evolution [and if we ever really will]. The more we learn about it, the more complicated it gets. Not too surprising, I guess, given the heavy burden it has to carry, generating all that species-level and individual variety, but from an engineering "I want to understand it so I can control it" standpoint, it's a bit daunting.


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