2.5: Tissue Patterning Flashcards
define differentiation
the acquisition of specialized cell functions (cell fates) via differential genome expression
t/f different cell fates require differential genome expression
true - through transcription regulators and regulatory modules
state the 2 different ways cell fates can be acquired and their description
- asymmetric division: daughter cells are born with different fates if you divide them correctly
- symmetric division then perception of a signal: daughter cells are born the same and acquire different fates as a result of different influences
which method of acquiring cell fate matches the following description: daughter cells are born with different fates if you divide them correctly
asymmetric division
which method of acquiring cell fate matches the following description: daughter cells are born the same and acquire different fates as a result of different influences
symmetric division then perception of a signal
asymmetric division evenly/unevenly partitions cell date determinants before division
unevenly
t/f most proteins and cellular components are distributed evenly (apart from cell fate markers)
true
in asymmetric division, one child cell will inherit more of what than the other cel
one child cell will inherit more of this cell fate marker than the other
what does asymmetric division require to occur
correct spindle alignment and cytokinesis
t/f only asymmetric divisions can create tissue patterns (and why do u think so)
false! both asymmetric and symmetric division can create tissue patterns because some cells symmetrically divide to create a field of similar cells and other cells divide asymmetrically to create several different cell types
some cells divide symmetrically to create a _______ of similar cells
field
list the two mechanisms on how cell fates can be acquired from symmetric division
- lateral inhibition
- induction by diffusible signals
the other ones are not discussed in this course
describe what lateral inhibition amplifies
- lateral inhibition amplifies small/stochastic (temporary) differences between cells
- both cells may start the same and a small/short/transient difference tips the balance
- molecular mechanisms will amplify these differences
= cells acquire different fates
what is notch signalling an example of
lateral inhibition
describe notch signalling in regards to symmetric division
- notch signalling is a form of lateral inhibition. lateral inhibition creates a pattern of isolated differentiated cells in a field of relatively undifferentiated cells
- each cells tends to inhibit its neighbor.
- each cells have a notch and delta tm prot. notch inhibits delta (same cell) and delta activates notch (other cell).
- activated notch inhibits cell specialization and inhibits delta expression
- at some point in the competition, one cells (cell1) wins and the c1 delta strongly expresses c2 notch. leading to no c2 delta on the activated notch’s (c2) cell which leads to no more delta on the opposing cell (c1).
- inactivated notch means the cell will specialize and will have delta
delta _________ notch signals and notch signals __________ delta expression
delta activates notch signals and notch signals inhibit delta expression
lateral inhibition creates a _________ of isolated differentiated cells
pattern
diffusible signals create a _______ or ______ pattern of differentiated cells
band or ring
describe how diffusible signals create a band or ring pattern of differentiated cells
- one of more cells in the organizer tissue secrete a morphogen
- morphogens are diffusible signals that can affect cell differentiation; they diffuse and act on nearby cells
- cells respond to the morphogen by taking on a new cell fate
- creates a pattern of bands/rings of different cell fates around the source
what type of tissue secretes morphogens/inductive signals
organizer tissue
what is the banding or ring pattern dependent on
alignment of organizer tissues
t/f cells can respond differently to the same morphogen given at different concentration
true - a morphogen gradient can form
list what the diffusion range of morphogens are dependent on
how much morphogen is made, for how long, diffusion rate of the signal, stability of the signal
t/f morphogens canNOT be indefinitely active and why
true - the cell remembers, you don’t need to keep telling it