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#permissive interaction

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Induction Morphogen -ll

Which of the following is an example of a permissive interaction?

Permissive induction occurs when responding tissue is already specified and merely requires a permissive microenvironment to execute its intrinsic program, rather than instructional patterning information. Epithelial cells pre-determined to differentiate need extracellular matrix components like laminin, collagen IV and entactin to support survival, polarity and transcription. Laminin binding to integrins activates FAK and ILK pathways enabling expression of milk proteins in mammary culture. In contrast, optic vesicle inducing lens or mesenchyme regionally instructing epithelium to form distinct structures exemplifies instructive interactions where new positional information is imposed upon competent responder.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 3: Permissive vs Instructive Induction and Extracellular Matrix.

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Induction Morphogen -ll

Which of the following is a feature of permissive interaction?

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.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 4: Permissive vs Instructive Inductive Interactions.

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