Practice question

Conditional specification signifies that final differentiated identity emerges from ongoing extrinsic instruction rather than intrinsic determinant inheritance. Cells continuously interpret local concentration of secreted morphogens, juxtacrine ligands like Delta, and extracellular matrix components, modulating intracellular pathways such as Smad, MAPK and beta-catenin to activate specific transcriptional programs. Classic cases include mammalian inner cell mass allocation to trophectoderm versus epiblast under position-dependent Hippo and FGF signaling, and amphibian ectoderm becoming neural under BMP antagonist gradients. This mechanism provides flexibility, regulation after damage and ability to compensate.