Cracking the DNA Code

. . . Leaves Mystery

Editorial / SF Chronicle 13feb01

FOR ALL the rigorous science devoted to mapping human genes, it turns out that there's plenty of mystery left. Big feet, a short temper or a gift for painting are human attributes governed partly by heredity. Everyone owes a debt to mom and dad.

But is that all there is? The world's top laboratory sleuths stepped back from a decade-long study of the human genome to announce that a deeper understanding of heredity lies beyond the genetic code under study. The numbers and computer-generated maps of our biological makeup don't explain everything.

It's a humbling thought for genetic science, but a reprieve for the rest of us. Experts originally believed that each human being carried upward of 100, 000 genes, making each of us a complex cocktail of uniqueness. The work suggested that laying bare the intricate makeup of DNA in chromosomes could explain disease, mental processes and general behavior.

More computer work dropped this number to 30,000, a figure in the same neighborhood as a mouse or worm or a grain of rice. How, then, is it that humans are more developed? One reason may be that the human gene sequences are more elaborate. Or that human proteins, needed for replication, can perform more functions than those found in other creatures. The genes in men and women, in effect, work harder.

But the wild card in careful scientific models is human conduct. Though genes can be important, human adaptability -- a sense of humor or a hunch to come in out of the rain -- plays a role in furthering the race. Humans may evolve for generations to live on mountaintops until one descendant decides to live near the ocean.

Genetics equip us all with the basics, but the chemicals don't do justice to the human they create. Something more, as yet unfound and unmeasured, explains the full range of human behavior.