MOLBIOL 3M03 Lecture Notes - Lecture 3: Proceedings Of The National Academy Of Sciences Of The United States Of America, Gene Regulatory Network, Oogenesis
15 Mar 2017
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This cleavage occurs in eggs with spare yolk and the holoblastic cleavage furrows extend through the entire egg. 1st 7 cleavages are stereotypic same pattern is followed in individuals in the same species. 1st and 2nd cleavage are both meridional and perpendicular to each other = cleavage passes through the animal and vegetal poles. 3rd cleavage is equatorial, perpendicular to the 1st two cleavage planes and separates animal and vegetal pole. 4th is different four cells of the animal tier divide meridionally into 8 blastomeres each with the same volume. Eight cells are called mesomeres vegetal tier undergoes an unequal equatorial cleavage produces 4 large marcomeres and 4 small micromeres. 16 cell embryo then cleaves with the 8 animal mesomeres dividing equatorially to produce an1 and an2 (staggered above one another) 6th division the animal cells divide meridionally while the vegetal cells divide equatorially.
