Developmental toxicology

The study of adverse effects on the developing organism that might result from exposure prior to conception (of either parent), during prenatal development, or from postnatal development to the time of sexual maturation.

Developmental biology

The study of the biology of normal development.

Developmental susceptibility gene

Any gene that encodes a gene product with which an environmental agent can interfere and cause a perturbation of normal development.

Drug metabolizing enzyme (DME)

Enzymes that metabolize endogenous substrates and also foreign chemicals. Among individuals, there are heritable differences in the catalytic activity of DMEs and in the ability to produce high levels of DMEs.


The study of the inherited basis of individuals’ different responses to environmental agents.

Ectopic expression

Expression of a gene in a tissue in which it is not normally expressed.


A means of introducing molecules into cells by transiently permeabilizing their membranes with a brief electric shock.

Embryonic stem (ES) cells

Permanent in vitro stem-cell lines derived from the undifferentiated cells of a very early, preimplantation mammalian embryo. They have the potential to contribute to all cells of a developing embryo when they are placed into an early embryonic environment.

Environmental factor

Physical, chemical, and biological agents or conditions encountered by humans, such as infections, nutritional deficiencies and excesses, life-style factors (e.g., alcohol), hyperthermia, ultraviolet radiation, X-rays, and the myriad of manufactured chemicals (e.g., pharmaceuticals, synthetic chemicals, solvents, pesticides, fungicides, herbicides, cosmetics, and food additives) and natural materials (e.g., plant and animal toxins and products).


A situation in which the phenotypic expression of one gene obscures the phenotypic effects of another gene.


Cells in which the genetic material is separated from the cytoplasm by a nuclear membrane.

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