Practice question

Radial cleavage pattern features blastomeres aligned directly above one another, mitotic spindles parallel or perpendicular to embryonic polar axis producing symmetrical tiered arrangement with blastomeres contacting one over other. Typical of deuterostomes such as sea urchins, starfish and chordates, it coincides with indeterminate development where isolated blastomere retains capacity forming complete embryo demonstrating regulative ability. Spiral cleavage characterizes protostomes showing oblique spindles and determinate fate. Radial cleavage therefore indicates deuterostome embryology and evolutionary link to regulative development enabling twin formation.