Cleavage and Its Types: Mechanisms, Patterns, and Developmental Significance in Animals
“ Cellular Choreography: How Cleavage Designs the Animal Body Plan” ✌Introduction Cleavage represents the earliest phase of embryogenesis following fertilization, characterized by rapid, highly regulated mitotic divisions of the zygote. Unlike somatic mitosis, cleavage divisions partition the cytoplasm without overall growth, resulting in progressive reduction in blastomere size while maintaining constant embryonic volume. At the M.Sc. level, cleavage is not merely a series of cell divisions—it is a tightly coordinated process that establishes embryonic polarity, cytoplasmic localization of determinants, and the foundation for body plan organization. ⚙️ Molecular and Cellular Mechanisms of Cleavage 1️⃣ Cell Cycle Modifications Early embryonic cell cycles differ from somatic cycles: G1 and G2 phases are shortened or absent. Rapid alternation between S phase and M phase. Regulated primarily by maternal mRNA and proteins stored in the oocyte. Cyclin-dependent...