Practice question

Conditional specification describes regulative development where final cell fate depends heavily on position within embryo and persistent interactions with neighboring cells rather than intrinsic inherited determinants. If isolated blastomere can form more than its normal fate and recombined embryos can regulate, intercellular communication dominates. Signaling via Wnt8, Delta-Notch, and other paracrine and juxtacrine pathways instructs neighboring cells to adopt endomesoderm versus ectoderm identities. In contrast autonomous specification relies on maternally deposited mRNAs and proteins. Sea urchin animal blastomeres exemplify conditional specification, requiring micromere signals to initiate gastrulation properly.