Gene-Environment Interaction Fact Sheet

Information from the Human Genome Project has caused scientists to re-examine the role of genetics and other risk factors involved in the development of disease. Understanding this complex interplay of genes and environment will leas us to new methods of disease detection and prevention.

Gene-Environment Interaction
	Virtually all-human diseases result from the interaction of genetic susceptibility factors and modifiable environmental factors, broadly defined to include infectious, chemical, physical, nutritional, and behavioral factors.

This is perhaps the most important fact in understanding the role of genetics and environment in the development of disease. many people tend to classify the cause of disease as either genetic or environmental. Indeed, some are diseases, such as Huntington or Tay Sachs disease, may be the result of a deficiency of a single gene product, but these diseases represent a very small proportion of all human disease. Common diseases, such as diabetes or cancer, are a result of the complex interplay of genetic and environmental factors.

Genetic Variations
Even so-called single-gene disorders actually develop from the interaction of both genetic and environmental factors. For example, phynylketonuria (PKU) results from a genetic variant that leads to deficient metabolism of the amino acid phenylalanine; in the presence of normal protein intake, phenulalanine accumulates and is neurotoxic. PKU occurs only when both the genetic variant (phenylalanine hydoxylase deficiency) and the environmental exposure (dietary phenylalanine) are present.