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#regulative development

3 public questions tagged with this topic.

Specification Determination-l

Which of the following is NOT an example of regulative development?

Regulative development examples include mammalian identical twins arising after splitting of inner cell mass into two embryonic axes, isolated sea urchin blastomeres forming complete larvae, and amphibian transplantation where presumptive epidermis grafted into neural plate adopts neural fate due to BMP inhibition. In all cases, remaining cells compensate for loss or altered position through inductive reprogramming and community effects. C. elegans development is opposite; lineage is essentially invariant, determinants partitioned rigidly, ablation permanently removes tissue. Such mosaic behavior lacks compensation and potency equals fate, illustrating autonomous rather than conditional regulation and not regulative development.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 3: Regulative vs Mosaic Examples.

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Specification Determination-l

Which experiment demonstrated regulative development in sea urchins?

Hans Driesch in 1891 performed landmark sea urchin blastomere isolation demonstrating regulative potential. By mechanically shaking apart two- or four-cell embryos, he found each isolated blastomere developed into complete, proportionate pluteus larva smaller than normal but correctly patterned. This unexpected outcome directly contradicted Roux mosaic results, proving fate not irrevocably allocated through cytoplasmic division. Remaining cells compensated via intercellular signaling respecification, establishing paradigm of conditional development and potency exceeding fate. Driesch experiment shifted embryology from deterministic preformationist determinant views toward modern concept of embryos as self-organizing morphogenetic fields governed by inductive interactions and positional information.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 3: Driesch Experiment and Regulative Development.

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Specification Determination-l

Which of the following is a characteristic of regulative development?

Regulative development emphasizes ongoing plasticity and environmental instruction of cell fate. Blastomere fates are not preassigned; instead, continuous dialogue via secreted morphogens, juxtacrine Notch signaling and mechanical cues guides differentiation and spatial organization. If cells are lost experimentally or embryos split, neighbors adjust gene expression to compensate, producing normal embryos or identical twins. Mammals, sea urchins and urodele amphibians illustrate this flexibility, enabling regeneration after ablation and self-organization of embryonic fields. Such regulative ability reflects potency greater than fate and characterizes embryos as dynamic adaptive systems rather than assembly.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 3: Regulative Development and Conditional Interactions.

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