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Biology 467 > Asymmetry > Flashcards

Asymmetry Flashcards

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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
Q

What kind of receptor makes up Johnston’s organ?

A

Mechanoreceptors

26
Q

What kind of sensory receptors make up the chordotonal organ?

A

Proprioceptors or mechanoreceptors

27
Q

Describe the attachment sites of chordotonal organs

A

Attach directly to the cuticle at exoskeletal joints, and between joints

28
Q

External sense organs have the appearance of…

A

Hairs

29
Q

What sensory modalities do external sense organs detect?

A

Touch/proprioception - limb position information and locomotor info

30
Q

How do external sense organs convey information to underlying neurons?

A

Deflection of the hair structure triggers a downstream response through movement

31
Q

Describe the origins of the hair, socket, sheath, and neuron in this image

A

All arise from a common sense organ progenitor cell

32
Q

How does intracellular notch know how to get to the nucleus?

A

It has a nuclear localization signal on it

33
Q

What is the role of p300 in Notch downstream signaling?

A

Promotes nucleosome acetylation which “relaxes” the chromatin so DNA is exposed and it can be transcribed

34
Q

Describe how lateral inhibition can play a role in Notch signaling and influence cell fate

A

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
Q

If there is a loss of Notch repression in a group of cells, what happens to them?

A

They all adopt the same fate

36
Q

Notch signaling was inhibited in all of the bottom panel cells. What is this image showing?

A

That when Notch is lost, more cells will adopt a neural fate (i.e. all cells fated similarly)

37
Q

How does Notch promote a proliferative state of progenitor cells?

A

It prevents differentiation and cell cycle exit

38
Q

What kind of epithelium (ie shape) is the neural tube when it is composed of neural progenitor cells

A

Pseudostratified neuroepithelium

39
Q

Who is Sauer (1935) and why do we care about him?

A

He examined developing chick neural tube and made very detailed histological/correlative observations about what was happening during development

40
Q

Who discovered interkinetic nuclear migration, in what year?

A

Sauer, 1935

41
Q

Define interkinetic nuclear migration

A

In the chick neural tube, cell bodies migrate towards the apical side and then divide

42
Q

How would you describe the diversity of the way in which retinal progenitor cells divide?

A

Orientation of cleavage furrow: some cells divide in the horizontal plane and some divide in the vertical plane

43
Q

What is the functional significance of having vertical versus horizontal cell divisions?

A

There might be something in the cells which is causing asymmetric division

44
Q

Describe the trends in symmetry in 1. horizontal and 2. vertical divisions in retinal progenitor cells

A

Horizontal: symmetrical daughter cells
Vertical: daughter cells of different size and shape

45
Q

What is the mechanism (name a specific molecule) which mediates asymmetric divisions in retinal progenitor cells

A

Numb!

46
Q

In a numb gain of function experiment where retina explants were administered excess Numb, what was different about these retinas?

A

They produced more photoreceptors than the controls

47
Q

In a numb/numblike double knockout experiment, what defects were present in these animals?

A

Had a premature depletion of progenitor cells and their neocortex and hippocampus were malformed (smaller nervous system)

48
Q

Based on the numb/numblike double knockout experiment, asymmetric numb distribution may be required for…

A

promoting proliferation over differentiation

49
Q

What is an imaginal disc in drosophila?

A

A sac-like epithelial structure which contains dormant rudiments of adult body parts, and during metamorphosis the tissues start to differentiate

50
Q

How long does the general process of neural patterning take in drosophila?

A

24h

51
Q

Mushroom bodies are associated with this function

A

Associative learning and processing

52
Q

Which part of the drosophila CNS contains motor neurons in development

A

Ventral nerve cord

53
Q

Describe the organization of each larval body segment in drosophila

A

Virtually the same organization

54
Q

Stereotypical pattern of muscle fibers in drosophila larvae are important for…

A

Coordinated inching movement

55
Q

Describe the proliferation capacity of a ganglion mother cell (GMC)

A

Limited proliferative capacity

Biology 467 (20 decks)

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