the relevant genotype of the individuals. The foregoing discussion about interactions has emphasized that it will be necessary for the genotypic information to be joined with environmental information. The identification of all of the relevant input variables for all health and disease issues will be a formidable undertaking. Fortunately, benefits will be derived from the partial knowledge that will be generated on the way. Increasingly, it will be possible for medical decisions to be informed by information about DNA as well as about environmental circumstances of the individual. Racial identity, at best a weak surrogate for these genetic and environmental factors, will become increasingly irrelevant in treatment of disease.
In broad terms, both genetic and environmental factors, particularly in interaction, play a role in racial and ethnic differences in health and disease. These factors are active subjects of investigation by the genetic and social sciences separately.
Research Need 5: Assess genetic and environmental factors in racial and ethnic differences in health simultaneously, in designs that permit identification of both main effects and interactions.
This research focus necessarily would emphasize the identification and assessment of environmental features, both physical and sociocultural, that are pertinent to ethnic differences in health outcomes. The range of environmental variables should be considered in a life-course perspective, with attention to the possibility of the existence of critical periods for environmental impact. Attractive research opportunities are offered by populations of particular ethnic groups in similar settings and life circumstances.
The potential value of concentration of research efforts on interactions is self-evident. If the incidence or severity of a disease related to a particular genotype is dependent on the environment, detailed examination of the mechanism through which environmental influence is mediated may suggest preventive as well as ameliorative measures. The advantages would accrue to individuals of all racial and ethnic groups.
Genetic comparisons among populations of course need to continue. Characterization of gene frequency differences among populations should be strongly oriented toward the detection of epistatic (interactive) gene networks, and the newly available molecular procedures for identifying and characterizing genes and evaluating the level of gene expression should be melded with quantitative methods for dealing with complex phenotypes.
As in all domains of biomedical research, although human beings are our targeted concern, some aspects of complex systems are most efficiently approached through animal models.