Genomic mappers navigate tricky terrain of race (NYT Science section)

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July 20, 2001 New York Times Science Section

Genome Mappers Navigate the Tricky Terrain of Race

By NICHOLAS WADE

Paul Hosefros/The New York Times

Dr. Francis Collins, director of the genome research institute.

WASHINGTON, July 19 — Scientists planning the next phase of the human genome project are being forced to confront a treacherous issue: the genetic differences between human races.

With the decoding of the human genome largely complete, government scientists are beginning to construct a special kind of genetic map that would provide a shortcut to locating the variant human genes that predispose people to common diseases.

The question the scientists face is whether that map should chart possible differences that may emerge among the principal population groups, those of Africans, Asians and Europeans.

Identifying the genetic variations that predispose people to diseases like cancer, diabetes and schizophrenia was a major purpose of the Human Genome Project. Most of these variant genes are thought likely to be the same throughout the world. But some may differ by population.

At a two-day conference that ended today, population geneticists and ethicists discussed whether the map should be constructed to explore these population differences.

Some speakers argued that the differences, even though obtained for medical purposes, might be used invidiously. Others said it would be wrong to exclude any group from the map if that meant they would not fully share the expected medical benefits.

The conference was organized by the National Human Genome Research Institute to plan the next phase in the process of interpreting the human genome. The genome sequence — the order of the three billion units of DNA that hold hereditary information — was obtained in draft form last June.

Dr. Francis Collins, the director of the institute, said it was important to set up the proposed map "in a fashion that benefits human kind and doesn't unwittingly do damage to one population or another."

The geneticists seeking to construct the map are working under the shadow of a previous proposal, called the Human Genome Diversity Project, which was intended to map the pattern of human migration out of Africa by analyzing the genomes of many peoples around the world. That project foundered after opponents said it would exploit the genetic patrimony of endangered peoples without addressing their more immediate health needs.

Geneticists said at the conference that the genome mapping project had very different goals and that different populations might be sampled to the bare minimum necessary to make sure the map was representative of everyone. Indeed, the first issue, they said, was whether to record the ethnic identity of the people whose genomes were sampled.

Most human genetic variations are found in all populations and presumably arose before the major population subdivisions produced after modern humans left Africa some 50,000 years ago. The roots of common genetic diseases are expected to lie in common variations that are found in all human populations.

Many of these disease-causing variants should be discoverable without having to search in specific population groups. But some population-specific variants may exist, and a population could fail to benefit if the variant is not detected.

Because scientists are not certain how disease-causing genes are distributed, the geneticists at the conference were divided on the need to keep track of ethnicity.

"In the end we may conclude none of those identifiers add much," said Dr. Eric S. Lander of the Whitehead Institute in Cambridge, Mass.

But Dr. Lander and others also sketched out the balance between helping and harming specific peoples.

"We must make sure the information is not used to stigmatize populations," Dr. Lander said. "But we have an affirmative responsibility to ensure that what is learned will be useful for all populations. If we shy away and don't record the data for certain populations, we can't be sure to serve those populations medically."

Dr. Thomas Murray, an ethicist who is president of the Hastings Center in Garrison, N.Y., said that to extend the medical benefits to everyone the project had to be inclusive.

"We don't have the luxury of blinding ourselves," Dr. Murray said, referring to the idea of ignoring ethnicity. "We have to say we want to be sure that all Americans get included in this."

Several speakers suggested that the information about different racial groups might in fact be helpful in showing how much of the genetic make-up is in fact held in common.

"If we educate the public properly it will undermine the traditional concepts of race, and race will begin to fall by the wayside in the traditional sense," said Dr. Phyllis Epps, a health lawyer at the University of Houston.

Dr. Lander said, "I think these data have tremendous potential to deconstruct simplistic notions of race and ethnicity."

The genomic map now being envisioned is called a haplotype map, and it is based on an emerging discovery that the cards in the human genome have been far less finely shuffled than was expected.

The genome, of course, consists not of cards but of chromosomes, each a gigantic DNA molecule of about 100 million units, or bases, in length. In each generation, the maternal and paternal versions of each chromosome exchange sections, shuffling the genetic material. The length of the unshuffled sections is an important consideration in trying to associate variant genes with the diseases they promote.

As the human genome was decoded, geneticists started looking for single bases that differed from the usual base at that position on the chromosome. These single base changes, called S.N.P.s or "snips," serve as markers to track variant genes, and can themselves be the cause of the variation.

Some 3 million S.N.P.'s have now been cataloged and in recent months scientists have found that the unshuffled sections of the genome are far larger than expected. A recent estimate predicted they would be an average of 3,000 bases long, but in fact many have turned out to be 50,000 bases or longer, a length that would cover several genes.

These long sections that contain several correlated S.N.P.'s are called haplotypes. Because of the large size of these haplotypes, geneticists believe it would be more useful to organize the growing collection of S.N.P.'s into their component blocks or haplotypes, with the goal of mapping these haplotypes across the genome. A haplotype map would speed the search for the variant genes that underlie disease.

Dr. Collins proposed at the end of the meeting that an international steering group be set up to decide how construction of the haplotype map should proceed and how it should sample the genomes of different population groups.



-- Lars (larsguy@yahoo.com), July 20, 2001

Answers

IMO, the genetics of race will be studied for the same reason that a dog licks its dick---because it can.

We already know that there are certain diseases that are more common in some races than in others (Sickle cell anemia in black Africans, MS in white Europeans). There are even disease tendencies unique to ethnic groups within a race (Tay-Sachs disease is found chiefly among descendants of white Eastern European Jews).

If there are genetic differences between races it will be important to identify them and understand their significance. It will be equally important not to deliberately distort or politicize this information.

-- Lars (larsguy@yahoo.com), July 20, 2001.


*I* sure hope that race isn't discarded in the research, Lars, and I don't think it will be. I'd be interested in the REASONS for some of these genetic anomalies. TO ME, it's pretty apparent that Africans have a greater chance of sickle cell anemia simply because it helped thwart malaria and was the best evolution could provide to keep the "line" going. Tay-Sachs has a less apparent cause. My ex-sister- in-law lived for about 10 years with a guy with Tay-Sachs. It wasn't fun to have another portion of one's colon removed every few years. Oddly enough, they split up because he wanted to reproduce and she didn't.

I don't think we can get away from the propensity of this or that happening based on our heritage, and information on how we got to be what we got to be is always interesting, IMO.

-- Anita (Anita_S3@hotmail.com), July 21, 2001.


Anita--

I saw a show recently on TLC channel about Neanderthal man. The show said that DNA had been recovered frpom Neanderthal bones (I didn't know that was possible) and it showed them to be significantly different fom Homo Sapiens. Both are hominids, but not the same species. Could they interbreed? The show fudged on that.

As you know, I have considerable affection for Neanderthals.

-- Lars (larsguy@yahoo.com), July 21, 2001.


Could they interbreed?

I highly doubt it, but you can keep trying. [grin]

-- Anita (Anita_S3@hotmail.com), July 22, 2001.


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