Wednesday, November 01, 2006

Here's a story you may have missed

At the urging of Craig Venter, the entrepenuerial genius who drove the sequencing of the human genome, the X Prize Foundation has announced that it will pay $10 million to the first privately-financed group to sequence 100 human genomes in 10 days. This is the same foundation that offered a $10 million prize for the first private company to fly a rocket into space and back twice in 10 days, awarded to Burt Rutan and his associates in 2004.

The genome challenge won't be easy. We are talking about 6 billion base pairs of sequence from the maternal and paternal components of the chromosomes, a listing that would fill more than two dozen sets of the Encyclopedia Britannica. The job will require staggering computer power and yet-unthought-of technologies. Will it happen? You bet. And sooner than you think. We are about to enter the age of the individual human genome. A decade from now, I'm guessing, you'll be able to have your genome sequenced for less money than you are now paying for a car, maybe those of your partner and offspring too.

There are four kinds of nucleotides along the DNA double helix: adenine, guanine, cytosine and thymine. Adenine always pairs with thymine, and guanine always pairs with cytosine: A-T, T-A, G-C and C-G. Four possibilities. The instructions for making a human self is written in a chemical code of just four letters.

Print out the sequence in 12-point type and you'll need a warehouse to store all those sets of books. You can spend the rest of your life combing through those volumes of four letters -- A, G, C, T -- for the differences that make the brown-eyed you different from your blue-eyed daughter.

Here's an analogy I worked out some years ago: Imagine the human DNA as strands of sewing thread. On this scale, the DNA in the 23 pairs of chromosomes in a typical human cell would be about 150 miles long, with about 600 nucleotide pairs per inch. That is, the DNA in a single cell is equivalent to 1000 spools of sewing thread! This represents two copies of the genetic code.

Take all that thread -- the 1000 spools worth -- and crumple it into 46 wads (the chromosomes). Stuff the wads into a shoe box (the cell nucleus) along with -- oh, say enough chicken-noodle soup to fill the box. Toss the shoe box into a steamer trunk (the cell), and fill the rest of the trunk with more soup.

Take the steamer trunk with its contents and shrink it down to an invisibly small object, smaller than the point of a pin. Multiply that tiny object by a trillion and you have the trillion soma cells of the human body, each with its full complement of DNA.

And soon you'll be able to buy a readout, assuming you are interested. The spine-tingling, mind-boggling score for the symphony of self.

But don't suppose the score is everything, any more than the score of Beethoven's Eroica is what you hear when played by an orchestra of world class musicians. Having your daughter's genome in a computer data bank is not the same as holding a human being in your arms. Not by a long shot.