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BIOL 303 Study Guide - Microtubule, Polarity In Embryogenesis, Neural Tube

Course Code
BIOL 303
Laura Nilson

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- benefits: egg big, develops quickly from fertilization to gastrulated egg and
then tadpole, amphibian eggs easy to obtain
- animal pole (dark pigment)
o cortical rotation; individual blastomeres; asymmetrical division
(smaller blastomeres at animal pole)
o Blastocoel forms separating animal cap from cells beneath it blastula
- Gastrulation
o Blastopore at grey crescent dorsal mesoderm then epiboly
(ectoderm moves down and surrounds vegetal region)
o Dorsal lip of blastopore (somites and notochord) to ectopic site
induces new axis therefore contains all necessary info to form a
complete axis
- Organizer: ability to become dorsal mesoderm; ability to dorsalize
surrounding mesoderm; ability to dorsalize surrounding ectoderm into
neural ectoderm; ability to initiate the movements of gastrulation and the
ability to cause the neural plate to become the neural tube
o Dorsal lip of blastopore = organizer
- How mesoderm is induced in blastula
o Animal cap + endoderm, get mesoderm
o w/o VegT, get blob of cells; Veg1 necessary as well
o D1-D4 vegetal blastomeres (endoderm) have different inducing
capacities (D1 = more dorsal and D3 more ventral mesoderm
- Cortical rotation is necessary for dorsal axis UV affects microtubules and
halts cortical rotation (active disheveled only at dorsal mesoderm and
stabilization of beta-catenin)
o If you take dorsal mesoderm and transplant rescues UV embryo
- Nieuwkoop centre endodermal cell that can induce dorsal mesoderm
o Only region containing TGF-beta signal and beta-catenin
o Able to INDUCE dorsal mesoderm in host
- Wnt signaling pathway canonical pathway
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