Asymmetry Flashcards

1
Q

In addition to giving rise to motor neurons, the pMNs of the neural tube also give rise to (2)

A

Oligodendrocytes and astrocytes

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2
Q

When is the earliest form of asymmetry established

A

Upon fertilization: sperm enters one side of the cell

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3
Q

Why are tunicates a worthwhile model organism to study?

A

They are chordates! Have a notochord and then lose it later in development

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4
Q

What is macho-1?

A

It is a transcription factor which is localized to the vegetal pole of an embryo and macho-1 positive cells are fated to become muscle

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5
Q

In an 8-cell embryo where normally only cell B4.1 expresses macho-1, what happens when the other cells undergo a macho-1 gain of function mutation?

A

All the cells develop muscle tissue

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6
Q

In an 8-cell embryo where normally only cell B4.1 expresses macho-1, what happens when you perform a loss-of-function experiment using macho-1 antisense knockdown?

A

All muscle tissue is lost

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7
Q

In an 8-cell embryo where normally only cell B4.1 expresses macho-1, loss and gain of function experiments determined that macho-1 is (1) and (2) for development of muscle tissue

A

Sufficient and necessary

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8
Q

Cell polarity is important for establishing (2)

A
  1. body axes
  2. tissue regionalization and subdivision
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9
Q

The first cell cleavage in C. elegans is…

A

Asymmetric

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10
Q

What mechanism is thought to mediate the first asymmetric cell division in C. elegans

A

Entry of the sperm into one side of the egg

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11
Q

When the sperm enters the posterior side of the egg, what does it “inject” into the egg?

A

Centrioles: start producing asters (cytoskeletal elements)

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12
Q

What is the name of the membrane marker which marks the sperm entry side of a fertilized egg?

A

Par2

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13
Q

Par-2 localization establishes the future (anterior/posterior) end of an embryo

A

Posterior

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14
Q

Define a p-granule

A

They are perinuclear (surround the nucleus) RNA molecules which are specific to C. elegans, but some other organisms have them

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15
Q

What is the role of p-granules?

A

Ribonucleoprotein complex (used for translation) which are necessary for specification of germ cells

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16
Q

What is a key role of PAR proteins such as Par2?

A

Aid in the cellular localization of p-granules around the nucleus

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17
Q

Segregation of p-granules in C. elegans embryo is always mediated by this molecule

A

Par-2

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18
Q

Describe cell division mapping in C. elegans, how does this contribute to its utility as a model organism?

A

Every cell division has been mapped which makes it a good model to study because we know so much about it

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19
Q

Describe the localization of p-granule cells as C. elegans grows and divides

A

P-granules always get segregated into a smaller and smaller cell because only the cells of the germ line will have these granules

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20
Q

At the 1-cell stage, asymmetric distribution of (1) cytoplasmic factors is one mechanism underlying cell fate determination

A

Intracellular

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21
Q

How might cell division influence asymmetry?

A

Asymmetric divisions have the ability to redistribute a given factor, this might be enough to trigger different cell fate of the two daughter cells - different “dosage” of intracellular components

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22
Q

What are the 3 key types of sense organs located superficially on the d. melanogaster body

A

External sense organs, Johnston’s organ, Chordotonal organs

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23
Q

Where is Johnston’s organ located?

A

Within the 2nd lobe of the antennae

24
Q

What is the role of Johnston’s organ? What sensory modalities does it detect?

A

They sense deflection of the 3rd antennal lobe - this allows the fly to distinguish between gravitational, acoustic, and mechanical stimuli

25
What kind of receptor makes up Johnston's organ?
Mechanoreceptors
26
What kind of sensory receptors make up the chordotonal organ?
Proprioceptors or mechanoreceptors
27
Describe the attachment sites of chordotonal organs
Attach directly to the cuticle at exoskeletal joints, and between joints
28
External sense organs have the appearance of...
Hairs
29
What sensory modalities do external sense organs detect?
Touch/proprioception - limb position information and locomotor info
30
How do external sense organs convey information to underlying neurons?
Deflection of the hair structure triggers a downstream response through movement
31
Describe the origins of the hair, socket, sheath, and neuron in this image
All arise from a common sense organ progenitor cell
32
How does intracellular notch know how to get to the nucleus?
It has a nuclear localization signal on it
33
What is the role of p300 in Notch downstream signaling?
Promotes nucleosome acetylation which "relaxes" the chromatin so DNA is exposed and it can be transcribed
34
Describe how lateral inhibition can play a role in Notch signaling and influence cell fate
When a stochastic event occurs and only one cell experiences Notch signaling, the responding cell can inhibit Notch signaling in neighbour cells and this can promote differential cell fate determination
35
If there is a loss of Notch repression in a group of cells, what happens to them?
They all adopt the same fate
36
Notch signaling was inhibited in all of the bottom panel cells. What is this image showing?
That when Notch is lost, more cells will adopt a neural fate (i.e. all cells fated similarly)
37
How does Notch promote a proliferative state of progenitor cells?
It prevents differentiation and cell cycle exit
38
What kind of epithelium (ie shape) is the neural tube when it is composed of neural progenitor cells
Pseudostratified neuroepithelium
39
Who is Sauer (1935) and why do we care about him?
He examined developing chick neural tube and made very detailed histological/correlative observations about what was happening during development
40
Who discovered interkinetic nuclear migration, in what year?
Sauer, 1935
41
Define interkinetic nuclear migration
In the chick neural tube, cell bodies migrate towards the apical side and then divide
42
How would you describe the diversity of the way in which retinal progenitor cells divide?
Orientation of cleavage furrow: some cells divide in the horizontal plane and some divide in the vertical plane
43
What is the functional significance of having vertical versus horizontal cell divisions?
There might be something in the cells which is causing asymmetric division
44
Describe the trends in symmetry in 1. horizontal and 2. vertical divisions in retinal progenitor cells
Horizontal: symmetrical daughter cells Vertical: daughter cells of different size and shape
45
What is the mechanism (name a specific molecule) which mediates asymmetric divisions in retinal progenitor cells
Numb!
46
In a numb gain of function experiment where retina explants were administered excess Numb, what was different about these retinas?
They produced more photoreceptors than the controls
47
In a numb/numblike double knockout experiment, what defects were present in these animals?
Had a premature depletion of progenitor cells and their neocortex and hippocampus were malformed (smaller nervous system)
48
Based on the numb/numblike double knockout experiment, asymmetric numb distribution may be required for...
promoting proliferation over differentiation
49
What is an imaginal disc in drosophila?
A sac-like epithelial structure which contains dormant rudiments of adult body parts, and during metamorphosis the tissues start to differentiate
50
How long does the general process of neural patterning take in drosophila?
24h
51
Mushroom bodies are associated with this function
Associative learning and processing
52
Which part of the drosophila CNS contains motor neurons in development
Ventral nerve cord
53
Describe the organization of each larval body segment in drosophila
Virtually the same organization
54
Stereotypical pattern of muscle fibers in drosophila larvae are important for...
Coordinated inching movement
55
Describe the proliferation capacity of a ganglion mother cell (GMC)
Limited proliferative capacity