Monday, August 17, 2009

The highest circle of spiraling powers

Among the exhibits of Boston's Museum of Science is a ten-foot-high model of a segment of DNA, spiraling upwards from floor to ceiling. The atoms are represented by colored balls -- carbon black, oxygen red, nitrogen blue, hydrogen white -- linked by rods. Whenever I used to visit, I'd stand in front of this partial strand of the code of life, gape-jawed at the beauty, at the simplicity, out of which emerges the astonishing diversity and awesome complexity of life. The museum's DNA model contains only several dozen base pairs, a tiny fraction of what is contained within the DNA of even the simplest living organism. If the whole of a human's DNA were shown at the scale of the model, it wouldn't fit within the entire museum.

I was thinking about that beautiful model when I was reading yesterday about the sequencing of DNA from fossil Neanderthal bones from Europe and Russia. Fossil DNA degrades over time into fragments just tens of base pairs long. Moreover, 99 percent of fossil DNA tends to be contaminated with the DNA of microbes and fungi that invaded the decaying bone. Nevertheless, with new highly-automated sequencing techniques and a lot of computer matching, Neanderthals are yielding their secrets. A complete Neanderthal genome was announced last year. Now, the mitochondrial DNA sequences of a half-dozen separate individuals have been completed. The samples show little genetic diversity across thousands of miles of territory. It has even been possible to estimate the total population of Neanderthals -- about 70,000.

This stuff is breathtaking. To my mind, the discovery of the double-helix, 4-letter code of life is the most stunning scientific discovery of all time. I was a high-school student when Watson and Crick's 1953 paper was published, and pretty much oblivious to anything but girls, but by the time I reached grad school the importance of the discovery was obvious to all: The whole of life, from microbes to humans, plants and animals, across the eons, share a molecular continuity.

If I had Bill Gates' money, I would donate one of those gorgeous ten-foot DNA models to every school that would take one, for display in the most public space, perhaps accompanied by this quote from Erwin Chargaff, who contributed mightily to unraveling the riddle of the genome: "It is the sense of mystery that, in my opinion, drives the true scientist; the same blind force, blindly seeing, deafly hearing, unconsciously remembering, that drives the larva into the butterfly. If the scientist has not experienced, at least a few times in his life, this cold shudder down his spine, this confrontation with an immense invisible face whose breath moves him to tears, he is not a scientist."