Practice question

Most vertebrate developmental processes rely on conditional specification because cells retain plasticity and continuously interpret environmental signals. Limb bud patterning employs FGF and Sonic hedgehog feedback loops, neural tube uses opposing Shh and BMP gradients, and isolated sea urchin blastomeres regulate to form complete larvae through intercellular communication. In sharp contrast, muscle lineage in C. elegans derives from early P lineage inheriting maternal determinants SKN-1 and PAL-1 that autonomously activate transcription factor hlh-1, the MyoD homolog, independent of neighbor signaling. Removal permanently deletes muscle, illustrating autonomous rather than conditional logic.