The Secret of Life

By NANCY GIBBS

Any 4-year-old who likes ladybugs and lightning bolts can tell you that life is wildly beautiful as far as the eye can see. But it took the geniuses of our time to reveal how beautifully ordered life is deep down where we can't see it at all--in the molecular workshop where we become who we are. James Watson and Francis Crick did not discover the existence of DNA; they discovered its structure, which means they unveiled its power as well as its beauty. If you could uncoil a strip of DNA, it would reach 6 ft. in length, a code book written in words of four chemical letters: A, T, G and C. Fold it back up, and it shrinks to trillionths of an inch, small enough to fit in any one of our 100 trillion cells, carrying the recipe for how to make a human being from scratch. The ingredients are the same for everything that lives; we are cousins to sequoias, and slugs--one life, one creation.

"The molecule is so beautiful," Watson once observed in a chat with TIME. "Its glory was reflected on Francis and me," and the two scientists have spent their lives since then trying to live up to its standards. They marveled that something so vital could be so simple and such a surprise. When they toasted their discovery in a pub one February night 50 years ago, Watson and Crick had no idea that not only biology but also the drugs we take and the machines we build, the food we eat and the choices we face when we decide to have a baby would be changed forever by what they had found.

Now, at the golden anniversary, we celebrate how much we have learned since then, including how little we know. For years scientists thought we human beings must have about 100,000 genes stitched onto our 23 pairs of chromosomes, only to discover that the number is less than a third of that. Like a vaccine against pride, the sublime achievement of the human intellect reveals that we have only twice as many genes as a roundworm, about three times as many as a fruit fly, only six times as many as bakers' yeast. Some of those genes trace back to a time when we were fish; more than 200 come directly from bacteria. Our DNA provides a history book of where we come from and how we evolved. It is a family Bible that connects us all; every human being on the planet is 99.9% the same.

On the other hand, we are learning that each letter in that text can spell the difference between blond and brunet, tall and short, life and death. A woman who carries a mutation in the BRCA1 gene can have a seven times greater chance of developing breast cancer. Scientists in Utah last week announced the discovery of a gene that seems to predispose carriers to depression. We are learning these things in part because of Watson, who, having revealed the simplicity of DNA's structure, wanted to explore the complexity of its function. He helped persuade Congress to fund the Human Genome Project, an attempt to decode the more than 3 billion letters of the complete human genome. Under competitive pressure from nimble private scientists, the goal was achieved ahead of schedule and under budget. In June 2000, when Bill Clinton and Tony Blair announced that the first rough draft of the genome was complete, Clinton declared that "without a doubt, this is the most important, most wondrous map ever produced by humankind." It was enough to fill 200 phone books at 1,000 pages each, or 75,490 pages of the New York Times. And it marked the turning point in the transformation of medicine from treating disease to preventing it altogether.

Each day now, as we discover where we are vulnerable, we move closer to designing drugs to protect us. Gene therapy allows doctors to introduce some handy gene into the body like a little rescue squad, to help produce enzymes that because of some faulty gene, the body can't make on its own. When we finally find cures for cancers, they will reflect the secrets of how our genes fight some cancers and yield to others. Drugs like Herceptin for breast cancer and Gleevec for leukemia work by blocking the chemical signal that tells the cancer to grow. They herald the day when we can look back on the traditional slashing and burning of cancer patients as having been as primitive as bloodletting.

And these new treatments are only a beginning. Genomics is already considered hopelessly 20th century by the scientists who have moved on to proteomics, the study of the proteins for which the genes provide the instructions. Since a typical gene may yield as many as 20,500 different kinds of proteins, scientists are only now figuring out how to begin to figure them out. Researchers don't even know how many proteins there are or how they fold, which means among other things that a whole new kind of machine is needed to study them. The new computers are coming to life. IBM models its newest ones--computers that act like cells and fix themselves wherever they break--after DNA. The quantity of information is so vast, we have to invent new numbers to measure it: not just terabytes (a trillion bits of genetic data) but petabytes (equivalent to half the contents of all the academic libraries in America), exabytes, yottabytes and zettabytes. All the words ever uttered by everyone who ever lived would amount to five exabytes. The speed of discovery leaves even our imaginations behind.

So many opportunities, so many cliffs to jump off--a new frontier of ethics, politics, religion and commerce. Centuries of philosophical arguments about free will are now twisted like that DNA strand. Are you truly free to be a size 6 if gluttony is in your genes? The nature-vs.-nurture debate changes when scientists find a gene that makes you shy, makes you reckless, makes you sad. For families haunted by generations of loss to cystic fibrosis and Tay-Sachs disease and sickle-cell anemia, prenatal testing may spare them a future as painful as the past. But if we can screen embryos for curses, should we also screen for gifts? Do you want to know if your child will have perfect pitch or violet eyes? Would parents love their children differently if they designed them to order?

Issues of privacy and knowledge arise every day, particularly as researchers develop tests that spot diseases for which there are no cures. Can it really be kept a secret from your boss or your insurance company or your future spouse that you carry a gene that predicts you will develop Alzheimer's by age 45? Would you want to know that you are likely to develop Huntington's disease if there is still nothing doctors can do to stop it from destroying you?

It is not only our genes we are learning to play with. What if we could create mosquitoes, those flying hypodermics, that instead of spreading malaria spread a vaccine protecting humans against it? Back in 1965, scientists fused mouse and human cells. Today whole animals are being patented; pigs are bred with human cells in hope of finding a source of organ transplants for the 70,000 people on waiting lists in this country alone. And that raises the question: If an Australian biotech company creates a creature that is part human, part pig, what law would apply to it? Should a company be allowed to patent a cloned human embryo, then market its cells to help fight disease? What if the embryo is made of human DNA planted in a cow's egg?

The first insecticide was made from powdered chrysanthemums in China nearly 2,000 years ago. Now biotech companies test bananas that contain a hepatitis vaccine and tomatoes that fight cancer. Dow makes a kind of corn that can turn into biodegradable plastic. Other companies have field-tested a cross between a flounder and a tomato to see if a fish gene can help a fruit stay fresh in freezing weather. The U.S. and the rest of the world are locked in a fight over how much to tinker with and how much to tell about what is now inside what we eat.

If the flip side to all this promise is the challenge that comes with it, perhaps it's a good thing that we may have a long time to weigh the answers. The more scientists learn about the way we age, the more they wonder why we have to. Our skin replaces itself every two weeks, our bones every seven years or so. With the help of the code book, maybe scientists will one day turn our bodies into repair shops, learn how to control the genes that break and those that fix, so that our lives, like the immortal molecule Watson and Crick deconstructed 50 years ago, go on and on...