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Early Development. Amphibians. Cleavage in a frog. Describe the progression of events. Gastrulation in Xenopus. What have fate maps told us about tissue origins?. Gastrulation in Xenopus. What are VegT and Vg1 and what influcence do they have?. Gastrulation in Xenopus.

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cleavage in a frog
Cleavage in a frog
  • Describe the progression of events.
gastrulation in xenopus
Gastrulation in Xenopus
  • What have fate maps told us about tissue origins?
gastrulation in xenopus4
Gastrulation in Xenopus
  • What are VegT and Vg1 and what influcence do they have?
gastrulation in xenopus5
Gastrulation in Xenopus
  • What type of cell movement initiates gastrulation?
gastrulation in xenopus6
Gastrulation in Xenopus
  • What happens next?
gastrulation in xenopus7
Gastrulation in Xenopus
  • What happens at the mid-blastula transition in preparation for gastrulation?
  • How is dorsal-ventral axis established?
  • What happens if cortical rotation is blocked?
gastrulation in xenopus8
Gastrulation in Xenopus
  • How did Gimlich and Gerhart demonstrate that certain cells were responsible for inducing dorsal lip formation?
gastrulation in xenopus9
Gastrulation in Xenopus
  • What appears to be the major factor directing movement of cells into embryo?
gastrulation in xenopus10
Gastrulation in Xenopus
  • What other cell movements occur?
gastrulation in xenopus11
Gastrulation in Xenopus
  • What two factors appear to drive convergent extension?
    • adhesion proteins paraxial and axial protocadherin are expressed
    • changes in calcium concentrations
gastrulation in xenopus12
Gastrulation in Xenopus
  • At what point in gatrulation do notocordal cells become distinct?
gastrulation in xenopus13
Gastrulation in Xenopus
  • What mechanism appears to be responsible for epiboly of the ectoderm?
axis formation
Axis Formation
  • How did Hans Spemann first demonstrate the importance of the grey crescent?
axis formation15
Axis Formation
  • What did Spemann do to demonstrate changes in cell potency during gastrulation?
axis formation16
Axis Formation
  • What classic experiment was done by Spemann and Mangold that led to the concept of the organizer?
axis formation17
Axis Formation
  • How did work of Nieuwkoop and Nakamura contribute to an understanding of how the “organizer” worked?
axis formation18
Axis Formation
  • What is the Nieuwkoop center?
  • How is it formed?
axis formation19
Axis Formation
  • What is involved in the mechanism of induction of mesoderm by endoderm?
  • What appears to be the role of β-catenin?
  • What is the connection between β-catenin and glycogen synthase kinase – 3 (GSK-3)?
axis formation20
Axis Formation
  • How does β-catenin become concentrated in dorsal cells of embryo?
axis formation21
Axis Formation
  • How does β-catenin contribute to formation of the organizer?
axis formation22
Axis Formation
  • What model was developed by Agius to explain mesodermal induction?
the organizer
The Organizer
  • What are the four major functions of this tissue?
    • differentiate into dorsal mesoderm
    • induce formation of paraxial mesoderm
    • induce formation of neural tube
    • initiate gastrulation movements
the organizer24
The Organizer
  • What is the role of the goosecoid gene?
the organizer25
The Organizer
  • How does the organizer actually induce formation of neural tissue?
the organizer26
The Organizer
  • What are the proteins secreted by the organizer?
the organizer27
The Organizer
  • What can the secreted protein noggin do?
  • What other proteins exhibit similar effects?
the organizer28
The Organizer
  • What are some of the important effects of BMP-4?
the organizer29
The Organizer
  • What are the functions of the diffusable proteins cerberus, dickkopf and Frzb?
  • How do these proteins work?
the organizer31
The Organizer
  • Why is neurogenin so important?
  • How did Otto Mangold demonstrate the regional specificity of neural induction?
  • Toivonen and Saxen postulated two gradients in amphibian embryos
    • dorsal gradient – “neuralizing” activity
    • caudal gradient – “posteriorizing” activity
  • What is the primary protein involved in posteriorizing the neural tube?
  • What positive signal promotes anterior head development?
left right axis
Left-Right Axis
  • What appears to be major event in left-right axis formation in Xenopus?