There are two categories of intercellular inducers; describe each category. What is the relationship between instructive and permissive inducers? Give an example of how the interrelated nature of these two types of inducers affect the developing embryo.
Instructive inducers, often secreted by the cells of the developing embryo, limit the developmental potential of a target cell by impacting a portion of its genome, thus, differentiating the target cell from cells not targeted by the chemical. Instructive inducers instruct cells as to what part of their genome they are to use. Permissive inducers, often hormones from the mother, tell cells to begin expressing a characteristic that has already been determined by an instructive inducer. For example, while instructive inducers commit cells in a male embryo to become the male genitalia, only in the presence of male sex hormone will those cells actually develop into the male genitalia. Without the hormone, the cells would develop into the female genitalia despite the fact that the embryo's sex is male. In this way, the male sex hormone present in the mother acts as a permissive inducer.
