An offspring’s normal development is governed by the genetic material inherited from the parental egg and sperm as well as environmental factors.

Genes influence our environment, and our environment influences the expression of our genes. Environment-gene interactions are also useful for understanding some diseases. Sometimes, sensitivity to environmental risk factors for disease are inherited rather than the disease itself being inherited. Individuals with different genotypes are affected differently by exposure to the same environmental factors, and thus gene-environment interactions can result in different disease phenotypes. For example, sunlight exposure has a stronger influence on skin cancer risk in fair-skinned humans than in individuals with darker skin.

Consequently, each of us represents a unique interaction between our genetic makeup and our environment; range of reaction is one way to describe this interaction. Range of reaction asserts that our genes set the boundaries within which we can operate, and our environment interacts with the genes to determine where in that range we will fall.

In another approach to gene-environment interactions, the field of epigenetics studies the same genotype that can be expressed in different ways. For instance, even if identical twins share the same genetic information, there remains an incredible number of variability in how gene expression can unfold throughout each twin’s life. Sometimes, one twin will develop a disease, and the other will not. The epigenetic perspective is very different from range of reaction because the genotype is not fixed and limited.

Key Points

• An offspring’s normal development is governed by the genetic material inherited from the parental egg and sperm, as well as environmental factors.

• Environment-gene interactions are useful for understanding some diseases.

• Range of reaction asserts that our genes set the boundaries within which we can operate, and our environment interacts with the genes to determine where in that range we will fall.

• Epigenetics studies the same genotype that can be expressed in different ways.

Key Terms

range of reaction: asserts our genes set the boundaries within which we can operate, and our environment interacts with the genes to determine where in that range we will fall

epigenetics: a study of gene-environment interactions, such as how the same genotype leads to different phenotypes

identical twins: twins that develop from the same sperm and egg