02 October 2006

There is no Nobel Prize for biology

But sometimes, physiology or medicine comes close.

This year's Nobel goes to the people who discovered RNA interference (RNAi). I never knew who developed that technique, though I've certainly heard a lot about it. Here's the deal.

In my introductory biology classes, I teach this simple little mantra: DNA makes RNA. RNA makes protein. Like so many things, that's a gross oversimplification, but it's a useful starting point. In particular, this little six word summary of what DNA does really underestimates the versatility of RNA. RNA has a structure similar to DNA, and actually binds to, and temporarily substitutes for, DNA in normal cell physiology. Or, for that matter, RNA molecules can bind together.

We know a lot about DNA. The traditional way that people figured out what different stretches of DNA did -- that is, what protein that bit of DNA ultimately made -- was to look at individual organisms with mutations. Very useful, but rather unpredictable, since it was usually hard to generate mutations at one point in the DNA only.

What RNA interference does is allows you to turn off particular bits of DNA that make particular proteins in a selective, controlled fashion.

Here's roughly how.

DNA makes RNA. A sequence of DNA has a code within it for a particular protein -- that's a gene. But DNA is stored in one place in the cell, and proteins are made somewhere else, so there has to be an intermediate. RNA is that intermediate. In particular, a type of RNA called messenger RNA binds to the DNA, makes a sort of mirror image copy of that gene. Then the messenger RNA goes off to meet with the protein making machinery. My understanding is that in RNA interference, an RNA molecule (usually experimentally chosen) binds to the messenger RNA, and breaks it apart, thus first obscuring, then destroying, the message the messnger RNA carried from the gene.

The Nobel for this discovery is interesting, because at this point, it's much more of an experimental technique than it is a basic discovery the unravelled something new about how cells work. There are definitely suggestions that RNA interference goes on in actual, living cells, but I think this is getting the prize much more because other scientists are finding it useful. In this sense, the selection is reminiscent of the award for polymerase chain reaction (PCR) some years ago.

And certainly, way down the road, it's easy to start imagining this technique being used to treat genetic disorders or perhaps certain viral infections.


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