Practice question

In Xenopus the first cleavage furrow is meridional, oriented along animal-vegetal axis passing through the sperm entry point initially but ultimately bisecting the newly formed gray crescent opposite entry. Equal bisection ensures both daughter blastomeres inherit dorsal determinants such as stabilized beta-catenin and Dishevelled concentrated by cortical rotation. This equal partitioning preserves dorsal potential bilaterally until later interactions restrict organizer activity dorsally. Subsequent cleavage planes alternate but first furrow's alignment with gray crescent is crucial for establishing bilateral symmetry and axial patterning.