Practice question

Permissive inductive interaction occurs when responding tissue is already specified toward a particular fate and inducing tissue merely provides supportive environment, nutrients, extracellular matrix or generic trophic factors enabling self-differentiation rather than conveying new positional information. For instance, many developing epithelia require underlying mesenchyme as permissive scaffold maintaining survival but retain intrinsic program without instruction. Instructive interaction contrasts by directly imposing new fate through specific instructive ligands qualitatively altering transcription including BMP inhibitors inducing neural fate. Permissive responses do not require quantitative dose of signal and show responder autonomy once specification achieved previously.