Practice question

Morphogens are universal patterning agents found across metazoa and even plants, not limited to vertebrates. Bicoid and Decapentaplegic pattern Drosophila embryo and wing discs, Wingless patterns imaginal discs and vertebrate limb, and auxin gradients pattern plant root and shoot apical meristems. They can function as secreted paracrine factors like Shh or as transcription factors like Bicoid that diffuse intercellularly after translation. Their gradients emerge early gastrulation to establish axes and they evoke distinct fate thresholds via enhancer affinity. Therefore claiming vertebrate exclusivity is incorrect and reflects misunderstanding of evolutionary conservation of gradient-based positional information.