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Human Genome News, July-Aug. 1995; 7(2):7

Colloquy Explores Genetic Predisposition

An Interdisciplinary Colloquy on Genetic Predisposition, organized by Pilar Ossorio (University of California, Berkeley) and Michael Yesley (Los Alamos National Laboratory) and sponsored by the Ethical, Legal, and Social Issues (ELSI) component of the DOE Human Genome Program, was held last fall in Washington, D.C. The diverse group of invitees included scientists; DOE and NIH grantees and staff; consumer group representatives; social scientists; philosophers; members of the NIH-DOE Joint Ethical, Legal, and Social Implications Working Group; and a theologian.

Francisco Ayala (University of California, Irvine) reviewed the meeting's purpose, which was to explore genetic predisposition from multiple perspectives and identify points of agreement and disagreement, questions for future discussions, and areas for policy development. Genetic predisposition was chosen as the topic because of its interdisciplinary relevance.

Referring to the nature-nurture controversy, Ayala discussed heritability and the extent to which genes and environment determine a particular trait. He said heritability is usually defined incorrectly as the contribution of genes to a trait, whereas a correct definition would be the contribution of genetic variation to phenotypic variation. Ayala pointed out that heritability can vary drastically from 0 to 100 for the same trait in the same organism. To illustrate his point, he used examples from biomass studies of a cinquefoil plant under varying natural conditions.

In his presentation on Gene Expression in Context, Chris Fields (National Center for Genome Resources) suggested looking at other disciplines for more precise concepts about genetic predisposition. He raised questions about the nature of genes and inheritance and suggested that a long-term, multigenerational view is needed when genetics is discussed.

Fields continued that experiments on model organisms in controlled environments don't reveal much about the range of gene expression and phenotypic variation in a natural setting. For the last 20 to 25 years, molecular biologists have used homogeneous model organisms and have studied biological mechanisms in controlled environments. Extrapolating from laboratory organism studies to the heterogeneous human population is not always possible.

Fields emphasized the need for scientific measurements and for a language that describes the level of complexity both in environmental action and in gene or other biological mechanisms. He believes biology is in a position analogous to that of physics in the last century, when a great deal of progress and optimism were prevalent but the conceptual foundation was only a year or two away from being completely rebuilt. He thinks biology is ready for a new foundation that couples the theory of evolution, which underlies all biological thinking, to the mechanisms of gene expression in a cellular, developmental, and environmental context.

Dorothy Nelkin (New York University) illustrated predisposition concepts that appear in popular culture. Beliefs in biological determinism from earlier this century are perpetuated today in the idea of genetic predisposition. A common theme is that people are not responsible for behavior because it is predestined by their genes. This theme also appears in discussions of alcoholism and other addictions, including smoking, overeating, and gambling. Now, Nelkin finds, some popular stories suggest that success and failure are encoded in genes. Popular assumptions about genetic predisposition oversimplify the complexities and contingencies expressed in scientific descriptions of these concepts. Deterministic assumptions about genetic predisposition are especially striking in American society, Nelkin said, where the very foundation of the democratic experiment is based on the improvability, indeed the perfectibility, of all human beings.

In his presentation on Genetic Predisposition and the Practice of Medicine, Eric Juengst (Case Western Reserve University) contrasted the metaphors of fortune teller and weather forecaster. He suggested that genetic predictions are probabilistic, like weather forecasting, and will vary according to local environment.

Juengst used illustrations to explain how people think about predisposition in the clinical setting and how patients see themselves. The major ways of understanding how people think about genetic disease and its social implications flow from two 19th-century models: "constitutional predisposition" and "specific causation." Environmental conditions may or may not be important in gene expression.

The group extensively discussed each presentation and the meaning of predisposition.


Participants recommended follow-up studies and discussions on predisposition and such related topics as informed consent, screening, and people's reactions to test results.

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