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#experimental model

2 public questions tagged with this topic.

Morphogen Induction-l

Which experimental model demonstrated that different morphogen concentrations activate different genes?

Lewis Wolpert introduced French flag analogy illustrating how uniform field of competent cells could generate three distinct stripes if exposed to graded morphogen where high triggers blue genes, medium triggers white, low triggers red. Model predicted threshold-based activation of different transcriptional programs, later validated using synthetic promoters with varying affinity for Bicoid or Dorsal and quantitative imaging of gap genes. Gurdon's nuclear transfer tested genomic equivalence and totipotency, Meselson-Stahl tested semi-conservative DNA replication, Griffith tested bacterial tran

Ref: Wolpert, Principles of Development, 6th ed., Chapter 5: French Flag Model and Threshold Genes.

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Morphogen Induction-l

Which of the following is an example of a morphogenetic gradient experiment?

Morphogenetic gradient experiments test dose-dependent fate induction rather than simple presence or absence of signal. In Xenopus, isolated animal cap ectoderm cultured with titrated recombinant Activin differentiates into ventral mesoderm at low dose, muscle at intermediate dose and organizer plus endoderm at high dose, recapitulating in vivo mesoderm patterning along vegetal-animal axis. This demonstrates diffusible factor encoding multiple fates by threshold via Smad2. Spemann organizer transplantation tests inductive capacity not quantitative gradient, CRISPR knockout removes gene but not

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 4: Activin Gradient Experiments and Morphogen Proof.

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