Mapping of Human Genes Requires Safeguards

Last year was a great year for gene hunters. New maps of the five feet of DNA coiled up in each human body cell have eased their job of linking specific genes (that is, specific bits of DNA) with specific human traits.

This is a big step forward for scientists. But as DNA mapper Thomas J. Hudson of the Whitehead-Massachusetts Institute of Technology Center for Genome Research in Cambridge, Mass., and his colleagues have noted, it still is only "an early step in an international project" to decode the master blueprint for the human body encoded in DNA. That is why legislation temporarily overshadowed by the US Congress's budget wrangles is so important.

A November bill introduced by Sen. Mark Hatfield (R) of Oregon would protect the privacy of an individual's genetic information. It would prohibit employers and insurance companies from using such information to discriminate against individuals. A similar bill by New York Rep. Louise Slaughter (D) would apply only to insurance companies.

That kind of protection is badly needed. Temptation is strong for some insurers and employers to rush to judgment about individuals whose DNA doesn't measure up to standards that currently seem "normal." Yet the effort to understand what biologists call the human genome - the master DNA blueprint - is in such an early stage that no one really knows what "normal" is.

Geneticists believe they have linked some bodily defects to certain genes. But other reported linkages, especially those related to behavior, are much more vague. The so-called "criminal" gene, for example, has been discredited. Also, many of the genes so far identified as defective only increase medical estimates of the probability of a disability or disease being manifested. They do not specify whether or when a specific individual would be affected. This is a poor basis for discriminating against individuals supposedly "at risk" for insurance or employment.

Gene hunting is a tricky business. The DNA molecule is like a ladder that is twisted into a helical shape. The sides are made of sugar and phosphate. The rungs are made of what chemists call bases. There are four of them: adenine (A), thymine (T), cytosine (C), and guanine (G). With that alphabet of four bases - A, T, C, and G - arranged along the DNA molecule like rungs on a ladder, all the information for building and maintaining living organisms is spelled out.

There are 3 billion of those "rungs" in the human genome. But only about 10 percent of them are believed to encode the information - that is, the genes - for making the proteins that determine body structure and functions. The functions of the rest of the genome are still obscure.

The DNA molecules making up this genome would stretch to five feet if laid end-to-end. They are packaged in 23 units called chromosomes. The international Human Genome Project aims eventually to decode all this DNA. Meanwhile, gene hunters try to locate specific genes on specific chromosomes, read their A,T,C,G sequences, and relate these to the gene's biological function.

To do this, they need maps that mark off parts of the genome into easily located regions. This is like a map of partly explored terrain that is marked off into distinctive regions without detailing what the regions contain. For the genome, the markers may be small DNA segments with distinctive A,T,C,G sequences. This kind of mapping made a major advance last year, with release of several improved versions. Dr. Hudson and his colleagues reported the most comprehensive of these maps last month in the journal Science. Their map is the first to cover 94 percent of the genome. It does so with unprecedented accuracy and precision.

With these new aids, the hunt to identify genes and their associated human traits will accelerate. Legal safeguards are needed to protect individuals from misuse of this rapidly accumulating, but only partially understood, information.

Temptation is strong for some insurers and employers to rush to judgment about individuals whose DNA doesn't measure up to current 'standards.'