lec 3- how cells in an embryo acquire different fates

Question 1

what is the name of development when cells retain the ability to alter their developmental course at relatively late stages of embryogenesis?

Answer 1

regulative development, meaning it can adapt to loss

Question 2

what is produced from regulative development?

Answer 2

cleavages produce daughter cells that are identical with undetermined and unlimited cell fates.

Question 3

what is it called when development occurs early in embryogenesis?

Answer 3

mosaic development, meaning it is usually already determined and cant change

Question 4

what is produced from mosaic development?

Answer 4

-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

Question 5

are developmental determinants (like proteins and mRNAs) asymmetrically distributed in a cell during mosaic development?

Answer 5

yes

Question 6

why is the unequal segregation of determinants into daughter cells also referred to as autonomous?

Answer 6

because each cell develops as though it were an independent self differentiating part

Question 7

what is conditional specification that occurs during regulative development?

Answer 7

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

Question 8

what happens when a cell receives a signal?

Answer 8

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

Question 9

what was roux’s conclusion?

Answer 9

from embryo is mosaic because the embryo developed its own role and didn’t compensate for the other dead half that was attached

Question 10

why was roux’s conclusion wrong?

Answer 10

his conclusion was wrong because he didn’t test it with the damaged part off, it could have still been sending signals

Question 11

when is development regulative in sea urchin embryos?

Answer 11

4 cell stage

Question 12

when is development mosaic in sea urchin embryos?

Answer 12

in the 8 cell stage

Question 13

what does the top half of the 4 cell embryo turn into?

Answer 13

animalized cells

Question 14

what does the bottom half of the 4 cell embryo turn into?

Answer 14

vegetalized cells

Question 15

what are the 3 ways a signal can be sent to other cells?

Answer 15

direct contact, diffusion, and gap junctions

Question 16

what does an instructive signal do?

Answer 16

tells the cell to get ready

Question 17

what does a permissive signal do?

Answer 17

guides the cell down its developmental pathway

Question 18

what does a diffusible signal do?

Answer 18

it conveys positional information that tells a cell if it should be pigmented or not

Question 19

what do cells perceive to gain pigments?

Answer 19

different levels of concentrations, above a threshold to gain certain pigments

Question 20

what is a morphogen?

Answer 20

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

Question 21

do morphogens induce multiple responses?

Answer 21

yes, not single

Question 22

what is lateral inhibition?

Answer 22

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

Question 23

what happens in a cell as it develops from an undifferentiated state into a specific cell type?

Answer 23

changes in gene expression regulate cellular differentiation during development