amphibian development Flashcards
what direction does cleavage happen in
animal to vegetal
are animal or vegetal cells larger
vegetal because they contain more of the yolk
where to the three tissue layers arise from
the ectoderm and mesoderm arise from the animal cap and the endoderm arises from the vegetal cells
how is the mesoderm induced from the animal cap
VegT (TF) activates nodal TGF beta which acts as a TF via the SMAD pathway to convert animal cells to mesoderm
where does gastrulation take place
at the dorsal lip between the animal and vegetal poles
which cell type induces the dorsal ventral axis
vegetal blastomere cells- dorsal vegetal cells induce the dorsal side and ventral vegetal cells induce the ventral side
what is the grey crescent
it is inherited by both the right and left sides of the embryo, it is opposite the sperm entry site and marks the future dorsal side- without in only the ventral belly will form
what is the Nieuwkoop centre
it specifies dorsal development of specific structures, and its formation is dependent on the Wnt pathway
what activates the Wnt pathway and how can addition alter the embryo
it is activated either by dishevelled Dsh or beta catenin. when added to the ventral vegetal embryo two dorsal sides will form
what inhibits the Wnt pathway and how can addition alter the embryo
is it inhibited by GSK3. when added to the dorsal vegetal embryo no dorsal side will form
where is the Spermann- Mangold organiser and how is it activated
it is located in the dorsal lip and is stimulated by the Nieuwkoop centre along with VegT
how is dorsal development stimulated or inhibited
it is stimulated by noggin and chordin RNA which is found on the dorsal side, and is inhibited by BMP4 (part of the TGF beta family) because it interrupts the SMAD pathway
why is BMP4 so problematic and how is it inhibited
it is a problem because it is dominant to chordin and noggin. it is inhibited by chordin or noggin binding to it and destroying it. this creates a concentration gradient of high ventral BMP and low dorsal, patterning the mesoderm and forming the DV axis
how does the ectoderm develop
it will develop to neural tissue by default, but will become epidermal tissue in the presence of BMP, patterning the mesoderm and forming the DV axis
