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BMS242 Developmental Biology > L8 - Germ Layer Induction and Gastrulation > Flashcards

L8 - Germ Layer Induction and Gastrulation Flashcards

(59 cards)

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1
Q

What is cell differnetiation

A

Process by which cells become different from each other and are able to acquire specialised properties

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2
Q

What is cell dif governed by

A

Changes in gene expression which dictate the repertoire of proteins synthesised

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3
Q

Describe extrinsic control

A

Cell non autonomous

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4
Q

Describe intrinsic control

A

Cell autonomous

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5
Q

Example of intrinsic control

A

Transcription factors

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6
Q

Example of extrinsic control

A

Morphogens

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7
Q

What does the ectoderm give rise to

A

Skin
Nervous system
Pigmented cells

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8
Q

What does the mesoderm give rise to

A

Muscle
Kidney
Blood

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9
Q

What does the endoderm give rise to

A

Lung
Thyroid
Pancreas

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10
Q

What layer gives rise to the sperm and egg

A

The germ layer

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11
Q

Gastrulation is best kniw through studies in ____

A

Xenopus

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12
Q

What occurs at the four cell stage

What does this give rise to

What are these two known as

A

Horizontal clevage

4 cells on the top, 4 cells on the bottom

Animal and vegetal cells

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13
Q

What are animal cells known as in chicks and human

A

Epiblast

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14
Q

What are vegetal cells known as in chicks and humans

A

Hypoblast

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15
Q

What is given rise to after the four cell horizontal cleavage

A

Morula

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16
Q

What is the morula

A

Hollow sphere of many cells which has a clear define animal and vegetal hemisphere

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17
Q

Where is the polarity in the oocyte seen

Why is this the case

A

Even before fertilisation

Due to gravity causing different cytoplasmic determinantns to sink to one part of the egg

Leads to the formation of the animal and vegetal pole

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18
Q

What is turned on in the cells in the vegetal pole

A

TFs come to be turned on in the vegetal pole - example of hich is Vgt

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19
Q

What is VgT

A

Vegetal- T-boc

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20
Q

Where is VgT localised to

A

Localised to the nucelus in the vegetal hemisphere cells

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21
Q

What does VgT bind to

What is the result of this

A

The promoter of nodal

Causes activation of Nodal

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22
Q

What is Nodal

Where does it act

How does it act

A

Secreted morphogen that can diffuse out of the vegetal cells into animal hemisphere

Acts on the cells in animal hemisphere were there are receptors

Activates the nodal signal trnasduction pathway

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23
Q

What is the effect of cells that recieve high nodal

A

Endoderm

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24
Q

What is the effect of cells that recicve intermediate nodal

25
What is the effect of no nodal
Ectoderm
26
Where is the Wnt pathway activated
On the dorsal side of the embryo
27
What does the point of Wnt activation mark for the future
Marks the future posterior dorsal part of the body
28
Where does sperm always fertilise the egg
Sperm always the animal side of the egg
29
What happens where the Wnt pathway is activated
Movements of gastrulaion begin
30
What forms directly opposite the point where the sperm enters
Organiser forms This is brought about by the fact that when the sperm enters the egg it initiates the rotation of the cortex
31
How many sides is the Wnt pathway activated
JUST the one side of the cell
32
What is the crucial TF involved wwith canonical Wnt signalling
B-catenin
33
What is the effeect of active Wnt singalling on B-catenin
Stabilises - allowing the entry of B-catenin to enter the nucleus and gene expression to be changed
34
What is the effect of B-catenin on Nodal
Increases levels of Nodal So transforms Nodal into a gradient
35
What is the region of overlap of Nodal and active Wnt
Nieuwkoop centre
36
Once Nodal has been transformed to a gradient what is it acting as
Morphogen
37
What occurs at the dorsal where Nodal is high
Forms the organiser
38
What forms at the ventral end where Nodal is low
Ventral mesoderm froms
39
Why is Nodal high at the dorsal end
Interaction of B-catenin (from active Wnt signalling) and VgT - gives high Wnt
40
Why is Nodal low at the ventral end
Only Vgt
41
The organiser forms under what conditions
Where cells recieve very high nodal and Wnt
42
What is the main gene expressed at the organiser
Gsc
43
Decribe the upstream enhancers of Gsc
Proximal element - Wnt/B catenin | Distal element - TGF-B/Nodal
44
Describe the conditions for when Gsc is produced
BOTH proximal and distal elements must be activate by Wn/B-catenin and TGf-B/Nodal
45
What do cells of the organiser differentiate into
Axial mesoderms
46
Describe the migration of axial mesoderm
Migrate collectively in a process called convergent extension
47
Why are different types of axial mesoderm cells produced
Siamois and Gsc are expressed at fractionally different leveles
48
Gastrulation is driven by movement of cells from __________ to _________
Posterior to anterior
49
What does the organiser undergo
Self differentiation
50
What does the organsier give rise to
Mix of progenitor cells Prechordal mesendoderm Prechordal mesoderm Notochord Together forming the axial mesoderm
51
What are the three main cell type of precurrsor form in the organiser region
Pharyngeal (anterior) endoderm Prechordal mesoderm Notochord
52
What is the shape of the involuting axial mesoderm
Rod shape
53
What does the axial mesoderm move over
Blastocoel
54
As the preaxial mesoderm moves what does it form
Fibronectin rich pathwya which binds to inegrins
55
Integrins are expressed on the
Organiser cells
56
The pahryngeal endoderm and the prechordal mesoderm mark the
Furture anterior part of the embryo
57
What are the last cells to migrate
The notochord cells
58
What do the notochord cells form
The future posterior part of the embryo
59
Explain how the blastocoel forms
At some point there is a change in osmolarity Results in an influx of water so morulla changes to a hollow sphere with a central fluid filled blastocoel

BMS242 Developmental Biology (17 decks)

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