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BMS242 Developmental Biology > L14 - Drosophila Appendage Development > Flashcards

L14 - Drosophila Appendage Development Flashcards

(67 cards)

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1
Q

Limbs are __________ patterned by ____________

A

Complex 3D structures patterend by conserved signalling cascades

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2
Q

Duplications of limbs is result of mutations due to a …

A

Defect in Hh signalling

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3
Q

What can be said about Hh signalling

A

Highlty conserved signalling pathway

Used in early patterning events and then again in limb development

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4
Q

How many instar stagges

A

3

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5
Q

Most of the adult tissue in drosophila is derived from

A

Imaginal discs

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6
Q

What are the imaginal discs made from

A

Diploid epithelial cells

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7
Q

What are the different immaginal discs

A 
Mouthparts
Antenna 
Eye
Leg 
Haltare 
Wing 
Genitalia
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8
Q

What does the number of discs depend on

A

The number of strcutures they go on to form

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9
Q

How many legs in drosophila

How many immaginal discs for the legs

A

6

6

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10
Q

When are the immaginal discs set aside

A

During embryogenesis

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11
Q

How can you see what the immaginal discs are

A

Using stains for specific marker genes

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12
Q

Describe what immaginal discs are seen in segments t1 - T3`

A

Leg - in all
Win - in T2
Haltare - in T3

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13
Q

Wing immaginal discs begins as a ____________

How many cells are they formed from?

A

2D epithelium

50000 cells

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14
Q

When do cells of the imaginal disc stop proliferating

A

At the third instar stage

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15
Q

What are the four segments of the wing disc

A

A P D V

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16
Q

The central region of the wing disc goes on to form the

A

Wing blade

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17
Q

The surrounding region of the wing blade goes on to form the

A

Hinge

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18
Q

What is the function of the wing hinge

A

Translate the force of the muscles which change the shape of the thorax into movements of the wing

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19
Q

What is responsible for forming the boundary between anteiror and posteiror

A

Patched gene expression (Hh)

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20
Q

What is reponsible for the formation of the boundary between dorsal and ventral

A

Wg gene expression

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21
Q

Nubbin gene expression is localised to the

A

Wing pouch

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22
Q

What type of gene is engraield

A

Segement polarity gene

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23
Q

Where is engrailed expressed

A

In the posterior of each segement

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24
Q

Describe the process used to visualse engrailed expression

A

LacZ expressed under the engrailed pormotoer
Use X gal
If there is LacZ present (forming B-galactosidease) Xgal gel goes from colourless to blue (insoluble)

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25
Results of the En-LacZ show that
En expressed in the posterior of all sgements | Very sharp boundary
26
Describe Hh signalling when there is no Hh ligand
``` Ptc represses Smo Smo unable to signal Ci to SuFu Ci to Cos 2 and Fu - interacts with 3 kinases - cleaved to a shorter repressive form Enters nucelus - represses target genes ```
27
Describe the Hh signalling pathway when Hh is bound
``` No repression of Smo Smo is phosphriylated Interaction with Ci and SuFU blocked Interaction with Ci and 3 kinases blocked Full length Ci enters the nucelus Acts as a transcritpional activator Causes transcription of target genes ```
28
What are some examples of Hh target genes
DPp Wg Engrialed
29
What is the function of en On ci On Hh
Causes promotion of Hh expresision Blocks expression of Ci
30
When is Ci expressed
In the absence of engrailed
31
Pathched is a .... and a ....
Receptor for Hh | Also a TARGET gene for Hh
32
What is the effect of Hh on Ptc expresison What is this known as
Increases expression of Ptc Positive feedback
33
Where is engrailed expression hi
P
34
Where is Ci expression hi
A Where there is no En
35
Descirbe the expression of Hh about the AP axis
High posterior | Diffusible molecule so diffuses into the anterior and a concnetration gradient is fomred
36
Where is engrailed not expressed
Anteriorly
37
To be competent to respond to hedgehog what must cells also be expressing
Ci
38
What is the effect of Hh on Ptc
Upregualtion
39
Dpp is a target ...
Of Hh signalling
40
What is the effect of Hh signalling of Dpp
Increased expression of dpp
41
What is the homologue of Dpp
TGF-B
42
Where is response to Hh seen
anterior compartment as these cells express Ci - only the ones that are in reach of Hh diffusion from the posterior
43
When Dpp is transcribed what is the effect of this
Dpp is also diffusible so another concentration gradient is establsihed going both anterior and posterior
44
Desribe the pathway of Dpp
Dpp --> Tkv/pnt --> Mad Mad --/ brn Mad --> Omb,sal
45
What is the active version of mad known as
p-mad
46
What genes do mad activate
Omb, Sal
47
What genes does mad repress
Brinked
48
What is Tkv/Pnt
Type1/type 2 receptor heterodimer
49
Describe the distribution of hh mRNA
Hh is localised to cells in the posterior that are seeing engrailed
50
What is the expression of Dpp mRNA
Expressed in a gradient based on Hh concentration gradient eastblished
51
What is the expression of p-MAd
Expressed in a concentration gradient since Dpp diffuses both anteriorly and posteriorly
52
How can you detect Dpp expression
Using a GFP fusion protein
53
Dpp acts as a ___________
Morphogen
54
What is the effect of high levels of Dpp
Sal and Omb expression
55
What genes are expressed by low Dpp levels
Only induce expression of Omb expression
56
What is a morphotrap
Expressing nanobodies which bind to a part of the morphogen preventing diffusion of the morphogen
57
Describe what morphotrap is used in the investigation of Dpp
Express GFP-Dpp Anti-GFP nanobodies (single chain AB) which are tethered to the membrane This traps dpp at the membrane where it is produced preventing the formation of a gradient
58
Describe the effects of GFP-dpp and anti-GFP which is membrane bound
Shows dpp expressed in the centre of the disc | No gradient formed
59
What was seen on the morphotrap when probing for p-mad
Dpp is held in the centre - cant diffuse away | Lack of a gradient of p-mad trapped in cells
60
What is the effect of p-mad on brinker
Repression of brinker
61
What is seen from the morphotrap when probing for anti-brk
Dpp expression represses the expression of Brk | Brk expression domains is expanded horizontally
62
Pathway from En to patterning
En --> Hh --> Dpp --> Patterning events
63
Describe what happens when a group of cells are transplanted into the anterior of the wing which are engrail (-/-)
``` Ci produced in group of cells (due to effect on engrailed from nearby cells) Hh from surrounding cells diffuses over Expression of Ptc and Dpp Dpp defines the midline Formation of an ectopic midline ```
64
What is the effect of transplanting a group of cells that express engrailed into the anterior
Engrailed - makes Hh No Ci Cells transplanted dont respond to Hh Hh diffuses to neighbouring cells (which express Ci and no Engrailed) dpp expresion and ectopic midline
65
What is the effect of putting a group of Ptc (-/-) into the anteiror
No supresison of smo by Ptc Hh signalling consitiutively active Even without the ligand still active signalling Act Ci enters nucleus in this group of cells - dpp induced - ectopic axis
66
Where there is an actopic activation and formation of a midline we see
Duplication of sturcutures
67
Describe the effect of putting Ptc KO cells at the boundary where Dpp is usuaully expressed
Ptc normally binds Hh Without ptc Hh can diffuse further Dpp expression shifted anteriorly

BMS242 Developmental Biology (17 decks)

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