Skip to content
Login Register

#tissue patterning

3 public questions tagged with this topic.

Morphogen Induction-l

The French Flag Model explains:

French flag model formulated by Lewis Wolpert explains how cells acquire positional information by interpreting concentration thresholds of a morphogen gradient from a localized source. Three outcome domains - blue high, white intermediate, red low - illustrate qualitative differences emerging from quantitative gradient readout via enhancer affinity. Model predicts identical competent cells adopt distinct fates depending on dose exposure. It underpins understanding of Drosophila Bicoid anterior gradient, vertebrate Shh limb and neural tube gradients and retinoic acid patterning, representing generic framework for concentration-dependent differentiation and pattern formation.

Ref: Wolpert et al., Principles of Development, 6th ed., Chapter 5: French Flag and Positional Information.

View Details
Morphogen Induction-l

Which of the following best describes morphogen function?

Morphogens encode positional information through concentration variation across tissue, converting analog gradient into digital transcriptional domains. Secreted source creates descending gradient; cells read local dose via receptor occupancy and intracellular effector activity such as Gli ratio for Shh or Smad phosphorylation for BMP. Distinct enhancer affinities cause different targets to activate only above specific thresholds, generating striped fate domains. This mechanism underlies Drosophila Decapentaplegic gradient, vertebrate limb Shh gradient and retinoid gradient, and is fundamental to embryonic axis patterning and French flag interpretation.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 4: Morphogen Definition and Function.

View Details
Specification Determination-l

Which of the following is a feature of morphogen-mediated cell specification?

Morphogen-mediated specification transforms continuous extracellular gradient into discontinuous pattern of distinct differentiated cell types arranged spatially through concentration-dependent responses. Cells possess receptors detecting graded ligand levels, converting dose into graded intracellular pathway activation such as phosphorylated Smad or nuclear Gli accumulation. Low dose may maintain progenitor state, medium induces one lineage, high another, due to cooperative enhancer binding and repressor displacement mechanisms. Limb bud Sonic hedgehog gradient patterning digits with posterior high specifying little finger versus anterior low thumb exemplifies principle. Thus single signal organizes field proportionally without requiring multiple inducers.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 4: Morphogen Concentration-Dependent Cell Fate Specification.

View Details