Practice question

Zebrafish development integrates both autonomous and conditional specification. Early cleavages segregate maternal dorsal determinants that stabilize beta-catenin and activate organizer genes autonomously, establishing initial axis. Subsequently, patterning of mesoderm, neuroectoderm and lateral line depends heavily on conditional signaling gradients of Nodal, FGF, BMP and Wnt that confer positional values, allow regulative compensation after cell removal and refine fates. This dual organization provides robustness and reproducibility, positioning zebrafish intermediate between extremely mosaic tunicates and highly regulative mammals, making them informative for studying transition from maternal to zygotic control and embryonic field organization.