The Human Genome Is Mapped
--Now What?

This morning at the White House, President Clinton announced that a consortium of public and private researchers has completed the first human-genome sequence map--a description of where each chemical lies in our DNA. Don't skip past this story as more techno-talk. It might be, oh, just roughly the most important announcement in human history.

For thousands of years, men and women have wondered how they are made; we are now poised to find out. Possession of genome-sequence information will make possible a huge range of good or evil developments, from breakthroughs in medicine and longevity, to loss of medical privacy, and perhaps much worse. Sequencing the genome means the beginning of the end for Homo sapiens as our species is now understood. Our near descendants may be called something like Homo geneticus, because the genus Homo is about to acquire the power to control its own evolution.

The human genome is the group of billions of molecules and 23 paired chromosomes that wind around each other in the double helix of DNA at the core of every human cell. The sheer volume of information stored in the human genome is enough to put the best computers to shame--about 3.5 billion "base points" of information, each formed by a chemical called a nucleotide and always found in pairs. If the DNA in any human cell were uncoiled and stretched out, it would be six feet long. Yet each of the trillions of cells in your body contains a version of this information--so elaborately shrunk and wrapped, it's difficult to see even with an electron microscope. The information in the human genome--the blueprint for a human life--if printed out as a book, would cover almost 200,000 pages--much longer than the full shelf edition of the Encyclopedia Britannica.

Everyone who thinks about the complexity of the human genome is stunned by its majesty, and this is an area of science where the more that is learned, the more majestic it seems. However the genome was made--divinely or naturally--this invisible object is the most marvelous and most important in our world.

What impact will the human gene sequence have? In immediate terms, it's only data. Now scientists have a map of which nucleotide is where, but they don't yet know what the map means. It's as if someone came into possession of a map of every road in the world but with all the destination names whited out, so you could tell where the roads are but not where they lead.

Where it all will lead is very much unknown. Though researchers now can say where all the "base pairs" of DNA are, they still have little idea what makes base pairs align into genes. (While the terms "DNA" and "genes" are used interchangeably, they're different: DNA are the units of biological code, while a gene is a group of DNA codes that cooperates to do something. Basically, the genome sequence tells a great deal about DNA but little about genes.) Researchers are still completely in the dark about how many total genes exist on the human genome--guesses range from 30,000 to 140,000 per cell, but both those numbers could prove way off.

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