BIO380H5 Study Guide - Midterm Guide: Posterior Pole, Cytokinesis, Paracrine Signalling
Document Summary
In mammals, the zygote undergoes complete cleavages to form the blastomeres: most insect eggs undergo superficial cleavage where a large mass of centrally located yolk confines cleavage to the cytoplasmic rim of the egg. In the fruit fly, nuclei initially divide without cellularization: this forms a syncytial embryo (a single cell with many nuclei residing in a common cytoplasm, karyokinesis (nuclear division) occurs without cytokinesis (cell division) Pole cells are segregated at the posterior: they will then become the future germ cells (gametes of the adult, nuclei becomes enclosed by cell membranes and generate the pole cells. Eight form the abdomen: first thoracic segment = legs, second thoracic segment = legs and wings, third thoracic segment = legs and halters (balancing organs) First step of gastrulation segregate mesoderm, endoderm and ectoderm. Mesoderm: folds inward to produce ventral furrow, furrow pinches off from surface to become tube.
