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Scientists warn of conceptual traps concerning "race" in new genetic map of human populations

by Lee Herring, Public Affairs Office, and Mercedes Rubio, Minority Affairs Program

Across the globe, the human genetic blueprint is 99.99 percent similar across individuals. But hopeful that the remaining variations may be predictive of an individual’s risk for particular disease and responsiveness to specific treatments, biotech researchers are inspecting these variations closely. The small remaining percentage of genetic variations notwithstanding, gene-based explanations for differences in complex social outcomes have been endemic to scientific and casual discourse since the 17th century.

Unfortunately, often-oversimplified discourse could become more prevalent following recent findings of a biotech research team from the California-based Perlegen Sciences, Inc. The potential for over-simplification prompted the scientists to publicly reiterate ASA President Troy Duster’s warnings at a Washington, DC, AAAS Annual Meeting press conference on February 17. Duster urged scientists and the public alike to be alert to conceptual illusions in the data and their potential to appear to endorse a gene basis for the social construct of race.

Genetic Signposts

What the Perlegen researchers successfully aimed to create was a detailed map of key genetic signposts (among subjects from three physically distinct human populations) in an effort to identify common disease-related DNA variations that might aid the development of effective, population-targeted pharmacological treatments. The scientifically naïve and even some biologists themselves may view Perlegen’s new map of human diversity as biological validation of socio-cultural delineations of racial categories.

Well aware of the potential for misinterpretation of the genetic data, AAAS editorial staff felt it necessary to include commentary in Science magazine from knowledgeable social scientists and to include this perspective in the press conference. Hence, a Policy Forum opinion piece, authored by Duster, accompanied the Perlegen scientists’ findings, which were published in the February 18 Science magazine (see “In the News” section of ASA’s homepage at www.asanet.org). The Science pieces received national media coverage including a story on National Public Radio’s February 17 edition of All Things Considered and extensive quotes of Duster in the March 3 Christian Science Monitor. The biotech firm’s scientists repeated Duster’s entreaty to not mistake the new findings as physical evidence that race exists at the level of DNA base pair combinations.

In addition to Duster (via phone), the AAAS press conference panel included Perlegen’s chief scientist David R. Cox, and geneticist David Altshuler of the Broad Institute at Harvard University and Massachusetts Institute of Technology.

The Haplotype Map

Specifically, the Perlegen researchers studied 71 people that included 24 European Americans, 23 African American and 24 Han Chinese Americans and found that within the researchers’ relatively small sampling of 1.58 million single-letter DNA variations, called SNPs (single-nucleotide polymorphisms), from among the 10 million such DNA site variations postulated, the study was able to capture most of the DNA sources of common human variation. As it turns out, most SNPs patterns have been preserved for thousands of years, despite the reshuffling of DNA that occurs with each new generation. The identification of these genetic variations (i.e., SNPs) may permit clinical scientists to more quickly and efficiently determine genetic risk for certain diseases and correlate treatment efficacy with a person’s individual gene patterns.

This research is part of a larger international effort to develop a haplotype map of the human genome. This “HapMap,” will allow researchers to more easily isolate genes and SNPs that affect health and disease. According to the U.S. National Human Genome Institute, sets of nearby SNPs on the same chromosome pass along to subsequent generations in chunks and are more likely to do so the greater their mutual proximity. This pattern of SNPs in a chunk is a haplotype. Chunks may contain a large number of SNPs, but a few SNPs are enough to identify the unique haplotypes in that chunk. The HapMap is a map of these haplotype chunks and the specific SNPs that identify the haplotypes are called tag SNPs. The HapMap’s value is to reduce the number of SNPs required to examine the entire genome for correlation with a phenotype from among the 10 million SNPs to the roughly 500,000 tag SNPs.

Lurking Illusory Intellectual Traps

When Duster spoke at the AAAS press conference, he reminded the scientific community that the “71 individuals do not represent all of the genetic diversity of their races, and that genetic differences would exist between any two small groups of people.” He also warned against “accepting the categories” that make it “easy [to] slide down the slope to misconceptions of ‘black’ or ‘white’ diseases.” He noted that “the first ethnic drug [BiDil]” is slated to get FDA approval in 2005 as an effective treatment against heart disease for African Americans. On average African American between the ages of 45 and 64 are 2.5 times more likely to die from heart failure than their White counterparts. On the surface, the differences suggest a biological underpinning; however, hypertension studies in the Caribbean show less racial disparities than in North America. If Blacks in the United States are presumed to be genetically similar to those in the Caribbean, then molecular genetics would indicate that that the root of the disease is not endemic to this socially contrived group. If anything, these findings suggest a complex interaction between social environment and genes.

What’s Next?

The efforts by scientists from biotech firms such as Perlegen or by pharmaceutical companies such as NitroMed (maker of BiDil) can, said Duster, “give a kind of imprimatur of scientific authority” thereby inadvertently fueling the lay public’s propensity to perceive innate racial differences as responsible for one’s health. According to Duster, this perpetuates the view that solutions lie strictly in medicines tailored to “specific races.” This outcome, said Duster, dangerously and inappropriately helps absolve social institutions, social arrangements, and public and social policies of any responsibility for the unequal distribution of disease across groups. Science and society will benefit from informed advocates helping to educate the public otherwise, especially since a more exhaustive and detailed description of human genetic variations is expected later this year from the international HapMap Project. This project is directed by government agencies in Japan, China, and Canada, as well as The Welcome Trust of London, and the U.S. National Institutes of Health. This mapping effort will describe variation across individuals of Japanese, Chinese, Nigerian, and European ancestry. Responsible scientists clearly have their work cut out too, apparently, to forestall nonscientists and scientists “misreading” the upcoming genomic maps in terms of imagined signposts of race categories.