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Playing with the Switches

Eventually, the breathless phase of genetics publicity will peter out, as more and more people - victims of illness, certainly - learn how hugely complicated the interaction of genes is. What do genes do, actually? Well, they trigger the production of proteins, and the body either changes or maintains accordingly. Until recently, it was thought that only a small percentage of our genome was still functional, because most genes don't trigger protein production in a body-building way. For a while, these "non-coding" genes were dismissed as "Junk DNA," leftovers from evolution. Now they're understood to be switches that activate or deactivate the genes that do produce protein. Tracking down the secrets of this ballet will make finding "the gene for blue eyes" seem like a kindergarten game.

A few weeks ago, H Allen Orr published an article in The New Yorker, "Is evolution facing a revolution?" that is not, unfortunately, online. Such a revolution, spearheaded by evolutionary developmental theorists (hence "evo devo") would account for the staggering similarity of genes from across species lines by highlighting the role that the "non-coding" genes play as switches. It is an elegant solution to be sure.

Evo devo's emphasis on switch-throwing represents a profound departure from evolutionary biology's long obsession with genes. Animal evolution works not so much by changing genes, Carroll maintains, but by changing when and where a conserved set of genes is expressed. In the lingo, evolution is regulatory (involving patterns of gene expression), not structural (involving the precise proteins coded by genes). ... Evo devo tells us that animal species look different not because their structual bits and pieces have changed but because they switch on and off the same old bits and pieces in different combinations. Roughly speaking, then, penguins and people differ for the same reason you pancreas and eye differ: they're expressing different genes.

If evo-devo is right, then it's going to be a long, hard slog to identifying the "genetic" causes of just about everything. There's an infinite-regression headache, too: non-coding genes throw their switches, presumably, at the instruction of other thrown switches.

In any case, it was with a deep chuckle that I came across a review, in the current Wilson Quarterly, of a study (conducted by political scientists, no less) of the genetic consequences of political orientation. Thanks to the miracle of twins, you don't have to be a biologist to romp in the fields of genetic extrapolation. Because twins share the same DNA, any difference between them must be attributed to something other than inheritance. Comparing differentials between twins with those of the general public ought to tell you something about the role that genetics has to play. Right? Well, not hardly. Because it is possible that certain switches are thrown by environmental factors - disease, perhaps, or fetal trauma. Bingo: not the same DNA anymore! But even aside from this objection, there's the apples-and-oranges aspect of trying to link up ultra-precise biological blueprints with the fuzzballs of political discourse. How do you frame meaningful questions for such an experiment? The review doesn't give any examples, but I don't think that it's possible to shortcut arduous physical research with such quickie "studies." And, oh, the loose talk about "blue state genes" that this could give rise to! A little knowledge is truly a dangerous thing.

And, yes, I understand that all knowledge is little.


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This is fascinating stuff, RJ. Thanks for the tutorial. I doubt I'll understand it any better than from your synopsis, but I'll pull my old New Yorker's and search out that article. It's rainy, cold, and dark tonight, perfect for catching up on my genetic reading. It all makes perfect sense, and so satisfyingly logical.

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