CSB328H1 Chapter Notes - Chapter 7: Polarity In Embryogenesis, Blastocoel, Lithium Chloride
22 Oct 2013
School
Department
Course
Professor
Document Summary
Chapter 7 sea urchins and tunicates: deuterostome invertebrates. This type of cleavage occurs in eggs with sparse yolk, and that holoblastic cleavage furrows extend through the entire egg. In sea urchins, the first 7 cleavage divisions are stereotypic in that the same pattern is followed in every individual of the same species. The 1st and 2nd cleavages are both meridonal and perpendicular to each other: that cleavage furrows pass through the animal and vegetal poles. 3rd cleavage is equatorial, perpendicular to the first 2 cleavage planes, and separates the animal and vegetal hemispheres from each other. 4th cleavage is very different: the four cells of the animal tier divide meridonally into 8 blastomeres, each with the same volume, these 8 are called mesomeres. The vegetal tier undergoes an unequal equatorial cleavage to produce 4 large cells macromeres and 4 smaller micromeres at the vegetal pole.
