Early Development Selected Invertebrates
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Transcript Early Development Selected Invertebrates
Early Development
Selected Invertebrates
Cleavage
What characterizes this process?
Cleavage
How does the cell cycle of blastomeres compare
with that of somatic cells?
Cleavage
What happens to the embryo during the
mid-blastula transition?
When does this occur?
Cleavage
What is karyokinesis and cytokinesis and how do
they compare?
Cleavage
What influences the pattern of cleavage in
a particular organism?
Cleavage
Cleavage
Cleavage
How are cell fates specified during
cleavage?
– cell-cell interactions
– asymmetric distribution of morphogenic
determinants
Gastrulation
What characterizes gastrulation in organisms?
What kinds of movements occur?
Axis Formation
What are the three major body axes?
Sea Urchin Development
What does the cleavage pattern look like?
Sea Urchin Development
What characterizes the blastula stage?
Sea Urchin Development
At what stage are the fates of individual cells
determined?
Sea Urchin Development
What role does βcatenin play in
specification?
Sea Urchin Development
Sea Urchin Development
When does axis specification occur?
– animal-vegetal axis established before
fertilization
– anterior-posterior axis determined by a-v axis
vegetal – determinants for posterior development
– dorsal-ventral and left-right after fertilization
d-v by first cleavage plane
Sea Urchin Development
How does gastrulation
begin?
Sea Urchin Development
What appears to be responsible for the
ingression of primary mesenchyme?
Sea Urchin Development
What appears to be responsible for the initial
invagination that occurs during gastrulation?
Sea Urchin Development
What is the fate of these vegetal plate cells?
Sea Urchin Development
What happens during later stages of
invagination?
Sea Urchin Development
Snail Development
What kind of cleavage pattern characterizes
these animals?
Snail Development
Orientation of
cleavage plane
determines right or
left coiling snails
Snail Development
What appears to be responsible for the mosaic
development seen in molluscs?
Snail Development
What is the polar lobe and why is it important?
Snail Development
Why does removal of the D blastomere or
its first or second derivatives result in
incomplete larvae?
If D blastomeres don’t directly contribute
cells to formation of many structures why
are they so important to the formation of
the same structures?
Snail Development
What other aspect of snail development
does the polar lobe influence?
– How do we know this to be true?
Snail Development
How does gastrulation take place in snails?
Tunicate Development
What makes these
organisms rather
unique?
What type of cleavage
pattern do they have?
Tunicate Development
In what way does the pigmentation in Styela
partita provide developmental information?
Tunicate Development
What evidence is there of autonomous
specification in tunicate blastomeres?
– transplant experiments
– RNA hybridization experiments
– altering β-catenin levels in cells
Tunicate Development
What evidence is there for conditional
specifiction?
– BMP signal from endoderm induces anterior
cell to become notocord
works through activation of Brachury gene
– FGF signal induces posterior cell to become
mesenchyme
Tunicate Development
When are the
embryonic axes
established?
– dorsal-ventral – prior
to first cleavage
– anterior-posterior –
prior to first cleavage
– left-right – first
cleavage
Tunicate Development
What is gastrulation
like in these
organisms?
Caenorhabditis elegans
What does C. elegans look like?
C. elegans
What pattern of cleavage in seen in this
nematode?
C. elegans
C. elegans
What determines
anterior-posterior
axis?
What is the
importance of the Pgranules?
C. elegans
When is dorsal-ventral and left-right axes
established?
C. elegans
In what way is autonomous specification
demonstrated in this organism?
– P1 develops without presence of AB cell
In what way is conditional specification
demonstrated?
– AB cell requires cell-cell interactions
– EMS requires signal from P2
C. elegans
cell-cell signaling
C. elegans
Where in this organism is autonomous and
conditional specification integrated?
C. elegans
When does
gastrulation begin in
this organism?