Biology 3338A Lecture Notes - Lecture 7: Archenteron, Spindle Apparatus, Mitosis
13 Nov 2016
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Cleavage: series of mitotic events that divide an egg cytoplasm into numerous nucleated cells called blastomeres. Cleavage rhythms are controlled by maternal factors. Mitosis has two components; karyokinesis and cytokinesis. Cytokinesis, contractile ring, actin microfilaments, cytochalasin b. Deuterostomes development, early cleavage division is radial. Zygote divides in half, quarters, eighths, dividing cytoplasm as it goes. spiral cleavage. Isolecithal is having an equal yolk, mesolecithal is having non-equal yolk. Telolecithal when cell division is on top of the yolk, they do(cid:374)"t ha(cid:448)e yolk. Ce(cid:374)trole(cid:272)ithal is (cid:449)he(cid:374) the yolk is in the middle, cytoplasm is not dividing and you end up cellularization around the nuclei (insect development) Radial cleavage you are coming right through the middle. Blastomeres are stacked and blastocoel is produced early. Rotational rotates in respect to eh cell you can get odd numbers of cells. Spiral cleavage is seen in molluscs and worms. Bilateral cleavage: first cleavage establishes left and right.
