Thursday, August 21, 2008

Knowledge and mystery -- Part 2

It strikes me that my last two posts have a lot in common. Basically, I understand how my new iPod works. Inside, it's just ones and zeros moving around from register to register under the control of stored instructions and a clock. Well, not ones and zeros, actually, but bits of electric charge or flip-flop circuits in one state or the other. Binary. On or off. Eight bits to the byte. A different byte for each stroke of the "keyboard." All that electric charge sloshing around at a speed of a billion sloshes per second. This is technology so advanced as to be indistinguishable from magic.

Meanwhile, in each of the trillions of cells in my body, an arm's length of DNA is running its own program. An arm's length of DNA distributed over 23 pairs of chromosomes. A double helix, spiral staircase. The railings are alternate sugar and phosphate molecules. The treads are pairs of organic bases, of just four kinds. Adenine, thymine, guamine and cytosine, designated A, T G and C. A always pairs with T, G always pairs with C. You can see a snip of the spiral, every atom, in the illustration here. Three billion treads in the human DNA. Three billion treads in every cell. Thirty thousand genes.

Not binary, but a four-letter code. Each three steps on the spiral can be in one of 64 states -- AAA, AAT, ATC, and so on. Twenty of these combinations code for the twenty amino acids of which all proteins are composed. Some other combinations do housekeeping. The DNA spins off messenger RNA. The RNA is a template for assembling proteins. You and I are big protein machines. More or less.

DNA and proteins interact. Tiny protein-based "motors" crawl along the strands of DNA, transcribing the code into single-strand RNA molecules. Other proteins help pack DNA neatly into the nuclei of cells and maintain the tidy chromosome structures. Still other protein-based "motors" are busily at work untying knots that form in DNA as it is unpacked in the nucleus and copied during cell division. Others are in charge of quality control, checking for accuracy and repairing errors.

A Tinker Toy set. But what a set! Talk about indistinguishable from magic! And the clock? The pacemaker? I look out my window into an overwhelming sea of life. Garden, fields, hedgerows, woods, reaching away to the horizon. Spiders, butterflies, cows, sheep, gulls, crows, invisible organisms in the sea and air. A panorama of teeming biological activity. All of those four-letter programs running continuously, inexhaustibly, creatively. Running ceaselessly here on Earth for 4-billion years, and for all we know throughout the universe. Running to the beat of a rhythm that has been humming at the heart of creation since the dawn of time.