lec 3- how cells in an embryo acquire different fates Flashcards
what is the name of development when cells retain the ability to alter their developmental course at relatively late stages of embryogenesis?
regulative development, meaning it can adapt to loss
what is produced from regulative development?
cleavages produce daughter cells that are identical with undetermined and unlimited cell fates.
what is it called when development occurs early in embryogenesis?
mosaic development, meaning it is usually already determined and cant change
what is produced from mosaic development?
-cleavages produce cells limited in developmental potential from asymmetrically distributed molecules that regulate development
-Daughter cells inherit different sets of of these determinants during cell division
are developmental determinants (like proteins and mRNAs) asymmetrically distributed in a cell during mosaic development?
yes
why is the unequal segregation of determinants into daughter cells also referred to as autonomous?
because each cell develops as though it were an independent self differentiating part
what is conditional specification that occurs during regulative development?
when the cells receive signals from neighbouring cells which determine their development, called it because the fate of the cell depends on the conditions in which it finds itself
what happens when a cell receives a signal?
signals received by a cell are transmitted to the interior of the cell via a signal transduction pathway with relay proteins causing the activation of transcription factors which can regulate gene expression to allow specification and determination
what was roux’s conclusion?
from embryo is mosaic because the embryo developed its own role and didn’t compensate for the other dead half that was attached
why was roux’s conclusion wrong?
his conclusion was wrong because he didn’t test it with the damaged part off, it could have still been sending signals
when is development regulative in sea urchin embryos?
4 cell stage
when is development mosaic in sea urchin embryos?
in the 8 cell stage
what does the top half of the 4 cell embryo turn into?
animalized cells
what does the bottom half of the 4 cell embryo turn into?
vegetalized cells
what are the 3 ways a signal can be sent to other cells?
direct contact, diffusion, and gap junctions
what does an instructive signal do?
tells the cell to get ready
what does a permissive signal do?
guides the cell down its developmental pathway
what does a diffusible signal do?
it conveys positional information that tells a cell if it should be pigmented or not
what do cells perceive to gain pigments?
different levels of concentrations, above a threshold to gain certain pigments
what is a morphogen?
a special kind of diffusible signalling molecule that forms a concentration gradient across a developing tissue and elicits different cellular responses that depend on the amount of morphogen the cell is exposed to
do morphogens induce multiple responses?
yes, not single
what is lateral inhibition?
when random cells start to form structures and are activated, these cells release inhibitory signals, the signal diffuses away from the cell creating an inhibitory gradient. Any cell within the range of the inhibitor will be prevented from forming a structure.
-activated cell sends out an inhibitory signal to inhibit neighbours
what happens in a cell as it develops from an undifferentiated state into a specific cell type?
changes in gene expression regulate cellular differentiation during development
