Developmental biology 2 Flashcards
(26 cards)
How does mammalian cleavage compare to that of C. elegans?
It is slower and occurs over days, unlike the rapid 1.5-hour cleavage in C. elegans
Why are mammalian eggs smaller than those of other species?
Mammals rely less on maternal factors due to the placenta and maternal-fetal blood flow
What type of cleavage is unique to mammals?
rotational cleavage
What does asynchronous cleavage mean in mammalian embryos?
Cells divide at different times due to differential transcription rates
What determines the fate of mammalian cells early in development?
Their position in the morula- inner cells become fetus, outer cells become placenta
When do mammalian cells lose totipotency?
Between the 16- to 64-cell stage.
true or false, mammals maintain totipotency longer than C. elegans
true
at the 64 cell stage, mammalian cells are _____potent
pluri
What structure forms from the compaction of the 8-cell embryo?
the morula
What happens during compaction?
Blastomeres flatten, upregulate E-cadherin for cell-cell attachment, and begin forming the trophoblast layer
what is the first epithelial layer?
the trophoblast layer formed after compaction
What is the zona pellucida’s role?
Prevents premature implantation in the fallopian tubes.
When does the zona pellucida shed?
At the blastocyst stage (4.5–5 days post-fertilization)
what does the trophoblast and ICm give rise to?
trophoblast layer = placenta
ICM = fetus
describe cavitation
- Na/KATPase on basal cell pumps Na+ into blastocyst, increasing osmotic pressure
- Cl-/HCO3- balance maintains electroneutrality
- Water moves into cavity via osmosis, causing the cavity to enlarge
Describe radial cleavage
generation of 2 polarised cells from one polarised cell from division in the radial plane
-> trophoblast giving rise to more trophoblast
describe tangenital cleavage
generation of 1 polarised and 1 non-polarised cell from division in the tangenital plane
-> trophoblast giving rise to ICM
by which mechanism does the trophoblast layer expand?
radial cleavage
- still no cell growth happening, still cleavage
what makes cells from the trophoblast polarised and cells in the ICM not polarised?
presence of microvilli on the apical surface of trophoblast cells
Can 16-cell stage morula cells be reprogrammed by new positions?
Yes, they retain some totipotency and adapt to new fates.
When is cell fate fixed in mammalian development
At the 64-cell stage, cells become either pluripotent or trophoblasts
are the trophoblast cells pluripotent at the 64 cell stage?
no, they are committed to the placenta
What directs cell fate after the 64-cell stage?
Positional information and cell-cell interactions
What is the purpose of tight junctions in the trophoblast epithelium?
To create a permeability barrier for water and molecule regulation
