ABSTRACT
Physical and personal traits underscore a basic dichotomy that also exists in the study of genetic variability and its role in disease. Certain genetic variations lead to outward manifestations of disease. Like physical traits (hair, eye and skin color, facial features, body build, and height), they are easily recognized by the physical signs they produce. However, it is the interaction between individual genetic compo sition and the environment that determines the most prevalent and important diseases affecting the broader range of humanity. The many diseases that result from gene-environment interactions are, like personal traits, far more complex to understand.
