lecture 10- post embryonic development Flashcards
(34 cards)
describe the 3 processed of how growth occurs and give examples of each
1) proliferation, in most cells
2) cell enlargement in muscle fibres under exercise
3) accretion, the deposition of extracellular matrix in bones
which CDKs and cyclins are present in each stage of the cell cycle
G1-Cdk 4 and 6 and cyclin D
S- Cdk2 and cyclin E
G2- Cdk2 and cyclin A
M- Cdk1 and cyclin A/B
which stage of the cell cycle do fully differentiated cells sit it
G0
in drosophila, what controls Cdks and cyclins?
string, a phosphatase
describe drosophila cell division up to cycle 13
no G1 or G2 phases
syncytium produced
maternally supplied string activates Cdks
describe cell division in drosophila from cycle 13 onwards
G2 introduced
nuclei migrate to edge of syncytium and become surrounded by an involuting cell membrane
now, depending on precise location, each cell develops its own division rate
string is expressed under direct control of patterning genes
what is cellularisation
where a multinucleated cell (syncytium) is divided into individual cells, each containing one nucleus and surrounded by a plasma membrane.
what is a mitotic domain
where cells undergo mitosis in a coordinated manner, both in timing and often in orientation, due to having similar cell fates
why is mesoderm tissue an exception to the string involvement process
it has string present but doesnt divide for ages
due to it having tribble, a string inhibitor
tribble promotes mesoderm invagination by preventing cell division
what is the difference between extrinsic and intrinsic control of organ size and give examples of each
intrinsic = organ knows what size it should be, hippo pathway
extrinsic = cues tell organ what size it should be, IGF signalling
does the thymus use intrinsic or extrinsic control and how do we know this
intrinsic
when transplanted into body with thymus already, it grows normally to a normal size
does the spleen use intrinsic or extrinsic control and how do we know this
extrinsic
when transplanted, it only grows to half the size
which is more important for organ growth, dimensions or number of cells
how do we know this?
dimensions
organs are the same size whether the organism is haploid or triploid
what does the TOR pathway do
increases cell size
what is the inhibitor of the TOR pathway
Rapa
what does the Hippo pathway do
limits organ size
describe the hippo pathway
pathway inactive= hippo or Mst1 inactive= YKi or Yap/TAZ in nucleus= growth and survival
pathway active = hippo or Mst1 active= YKi or Yap/Taz out of nucleus= no growth
how is the overall size of an organism controlled
with the GH / IGF1 pathway
also due to maternal environment
what is the proof that maternal environment has an impact on growth
women that have been malnourished during pregnancy have babies with increased diabetes
how is molting/metamorphosis controlled
by short range signals
environment ->CNS -> hormones
describe molting in arthopods
1)molting initiated by activation of stretch receptors in the cuticle
2)release of protothoracicotropic hormone from corpus alatum
3)release of ecdyson from protothoracic gland
4)cuticle seperates from epidermis
5)freed epithelial cells proliferate and secrete a fluid forming a barrier to make new cuticle
6) old cuticle sheds
describe metamorphosis in frogs
corticotropin releasing hormone secreted
TSH secreted
T4T3 activated
what causes metamorphosis to be irreversible
the processes positively feed back on eachother
which tissues is cancer the most common in
tissues dividing through life as there is a higher level of division
