Where will DNA map lead us?

Scientists announce that they now have a rough draft of the human genetic code.

Are human beings merely the sum of their genes?

That question commands humanity's attention with today's scheduled announcement that scientists have developed "rough drafts" of a human's genetic blueprint - the human genome.

Just as 19th-century scientists placed chemical elements in a descriptive framework - the periodic table - and helped pave the way for many of the 20th century's scientific revolutions, biomedical researchers expect the sequenced genome to spark a 21st-century revolution in human biology and medicine.

Even before the rough draft's gaps have been filled and errors reduced, researchers have started to identify individual genes and their functions. That effort is already leading to technology that could change conventional therapies.

Over the longer term, scientists are working toward treatments that repair or replace genes deemed faulty. In principle, some researchers say, understanding genes and the role they play - singly or in combination with other genes - eventually could lead to genetic treatments that augment or enhance human functions such as hearing or sight.

Yet others urge caution. They hold that the promise of medical advances may be premature, and that the glamour of gene therapies may obscure cheaper, more cost-effective approaches to treating many diseases. In addition, they say, an emphasis on genes could lead to a broader definition of what constitutes illness - defining human health by probabilities based on the genes people carry instead of whether a malady actually manifests itself.

This redefinition raises concerns about employers or insurance companies discriminating against people because they carry gene mutations associated with a certain disease. It also has led ethicists and scientists to caution against overstating the role genes play in who we are.

"We have to educate physicians and the general public" about how genetic information should be used and interpreted, says George Annas, chairman of the health law department at Boston University's School of Public Health. "We are not our genes."

He says education about the limits of genetic information - amid inflated expectations of its promise - is part of the defense against lapsing into genetic determinism.

"Genes matter," adds Ruth Hubbard, professor emerita of biology at Harvard University and adviser to the Council for Responsible Genetics in Cambridge, Mass. "But what really matters is the relation between genes, and between genes and other elements that make up us."

Many of these concerns and ethical questions have been around for years, but now that we have a rough draft of the genome, the pace of discovery - and efforts to get those discoveries to market - is likely to increase.

"Once you understand the building blocks, you can describe processes and predict properties," says Richard Young, a professor of biology at the Whitehead Institute and at the Massachusetts Institute of Technology in Cambridge. "Once you understand the building blocks, it leads to extremely rapid advances."

Now that the sequence of chemical building blocks has been sketched, new technologies are being introduced, he says, that will greatly speed the process of identifying individual genes - the next major phase of the Human Genome Project. "If you'd asked me three months ago, I'd have said this is a 20-year project. Now I think it will be done in about six years."

Even so, the task is daunting: Researchers must sort through some 3 billion pairings of four chemical compounds, or nucleotides.

These nucleotides form DNA, a molecule that lies in the nucleus of cells. Genes are segments of the DNA molecule that carry the instructions cells need to function. Each nucleus contains a complete complement of human DNA, although a cell may need only a relative handful of genes to do its work.

The human genome holds an estimated 80,000 to 100,000 genes, although Dr. Young notes that no one really knows how many genes there are.

While the quest to understand the human genome continues, some skepticism remains about whether its medical potential - particularly for gene therapies - will live up to its billing.

"We keep hearing that perhaps, eventually, there will be benefits to health - that once we understand the DNA basis of disease, it will become easier to treat or prevent. But is that true? That's an open question," says Dr. Hubbard. "For years, we have had the complete DNA readout of HIV, but that hasn't made it any easier to deal with HIV or the manifestations of AIDS."

What effect it will have on how we view identity is also a question of increasing urgency, say others.

"Are we prisoners of our genes? The answer to that question is very important. It affects our thinking about human nature," says Arthur Caplan, director of the Center for Biomedical Ethics at the University of Pennsylvania in Philadelphia.

For the Whitehead Institute's Young, there's much more to learn before we understand any how genetics and related.

"There's a reductionist approach to science, where you break things into their smallest bits and try to understand them," he says. "But those small bits will never fully describe how complex systems work. Once we have the genome, we still won't be able to tell you what fraction of behavior or character comes from your genome, because we're not equipped to understand the combined effects of 100,000 genes in each of 10 trillion cells."

(c) Copyright 2000. The Christian Science Publishing Society

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