Ecogenetics: The Study of Gene–Environment Interactions

Abstract

What is “an environmental disease?” Why are some individuals and some families affected more easily than others? Indeed, even within families, why are some members affected whereas others are not? When taking the same dose of a prescribed medication, why do some patients—but not others—experience side effects? Why do only 7 out of every 100 cigarette smokers die of lung cancer? The answer to each of these questions involves interindividual genetic variation and the environment. We begin this chapter with brief descriptions of the reasons for environmental illnesses. Next, genetic terminology and a definition of “susceptibility genes” are covered—followed by our current understanding of the drug-metabolizing enzymes (DMEs) and the receptors that regulate DME genes. Subsequently, we provide a number of examples and brief summaries of the present-day knowledge of many of these polymorphisms. Last, we speculate as to why these human polymorphisms might exist in the first place. Many of the references cited include reviews in which the reader will find numerous additional studies cited and details described. Keywords: Genetic predisposition; Genetics; Traits; Polymorphism; Human genome; Reverse genetics; Forward genetics; LOD scores; Environmental genetics; Susceptibility genes; Drug metabolizing enzymes; Ecogenetic differences; Adaptation; Synergy