Flashcards in Cleavage Deck (34):
What are a few things that Cleavage accomplishes?
Multicellularity, regionalization, cell-cell interaction and movement, partitioning of localized determinants
What is different between the somatic cell cycle, and the embryonic cell division cycle?
There are no gap phases [g1 and g2] in the embryonic cleavage cycle
Describe the cleavage division cycle as it pertains to cyclin
Cyclins are synthesized, attached to cdc2 for MPF in the M phase, then degraded in the S phase. This repeats
Each successive cleavage does not really alter total volume of the blastula
What is the contractile ring mostly made of?
What is the role of astral microtubules during cleavage?
They align the cleavage furrow and spindle mid zone for the contractile ring
What precedes actin polymerization at the contractile ring?
The protein Rho
What happens if you block Rho?
There will be multiple nuclei, but no cleavage.
How can you block Rho?
With C3 transferase
What is the major challenge to increasing the surface area/volume ratio?
You need more membrane
Where is new membrane inserted?
At the furrow
uniform, not a lot of yolk
moderate, slightly more yolk on one end
Lots of yolk, usually at one end
yolk in the middle
What are the main orientations of cleavage?
Radial, spiral, bilateral, rotational, discoidal
Cleavage[description,examples]: Holoblastic,Isolecithal, Radial
Annelids, mollusks, flatworms
Cleavage orientation is determined by:
If cells contain less yolk, they tend to be
smaller, and toward the animal hemisphere
Where does the blastocoel tend to form?
At the place with the less yolky cells
How does the blastocoel create a different ionic content?
Tight Junctions seal off the coel
What is a blastoderm?
In mesoblastic chick eggs for example, the cell sheet on top of the yolk