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Neuroscience Y2S1 > Building Brains 5 - Vertebrates > Flashcards

Building Brains 5 - Vertebrates Flashcards

1
Q

Describe what happens between fertilization and formation of the blastocyst in the early vertebrate embryo. (2)

A
  • Cells proliferate
  • Cells compact
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2
Q

Name the two structures present in the blastocyst stage of the early vertebrate embryo. (2)

A
  • Trophoectoderm
  • Inner cell mass
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3
Q

In the blastocyst of the early vertebrate embryo, what structure/s are formed by the trophoectoderm? (1)

A

Extraembryonic tissue, eg. placenta

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4
Q

Name the two layers which form from the inner cell mass of the early vertebrate embryo.

What does each layer form? (2)

A
  • Epiblast (forms adult cells)
  • Hypoblast (forms extraembryonic tissue, eg. yolk sac)
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5
Q

Complete the sentence regarding the development of the early vertebrate embryo. (2)

The two layers of the inner cell mass, the epiblast and hypoblast, detach from the trophoectoderm to develop as a disk. This structure is now called the ………………………… The entire embryo is now called a ………………………

A
  • Blastodisc
  • Gastrula
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6
Q

Name the process by which the three germ layers are formed in the early vertebrate embryo. (1)

A

Gastrulation

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7
Q

Describe the order in which gastrulation occurs in the early vertebrate embryo. (1)

A

From posterior to anterior

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8
Q

Describe the structure, location, and role of the primitive streak in the early vertebrate embryo. (3)

A

Groove

in the dorsal embryonic midline

which is the site of gastrulation.

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9
Q

Describe the process of gastrulation in the early vertebrate embryo. (4)

A

Cells from the surface of the epiblast migrate towards primitive streak

then move down and out

first integrating into the hypoblast layer to form the endoderm

then sitting between the endoderm and ectoderm to form the mesoderm.

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10
Q

True or false? (1)

In the early vertebrate embryo, the primitive streak establishes the anterior-posterior axis.

A

True - however this may not apply to humans

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11
Q

In the early vertebrate embryo, the primitive streak establishes the anterior-posterior axis.

Name two other ways that the axis may be determined in the embryo. (2)

A
  • Gravity
  • Point of sperm entry into egg
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12
Q

Describe the ‘movement’ of the primitive streak throughout development in the early vertebrate embryo. (3)

A
  • The primitive streak extends towards the head
  • Then regresses posteriorly after reaching full extension
  • Then disappears
  • As the primitive streak regresses it leaves the notochord in its wake
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13
Q

Describe the migration of the cells during gastrulation, which end up forming the notochord in the early vertebrate embryo. (1)

A

The notochord is formed by the cells which have passed through the node

at the anterior end of the primitive streak.

They are the last cells to migrate.

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14
Q

Name the process which forms the neural tube in the early vertebrate embryo. (1)

A

Neurulation

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15
Q

Describe where neurulation begins in the embryo and how it progresses. (1)

A

Begins anteriorly and progresses posteriorly.

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16
Q

True or false? (1)

When looking at the embryonic nervous system at a single point in time, the posterior part will always be more developed than the anterior part.

A

False - the cranial nervous system develops before the caudal nervous system, so the anterior part will be more developed

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17
Q

Describe the stages of neurulation in the early vertebrate embryo. (4)

A
  • Neural plate thickens
  • Neural plate bends in dorsal midline
  • Two ends of neural plate join at neural plate borders to form a tube
  • As tube closes the neural crest disconnects from epidermis
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18
Q

Where does the notochord sit in relation to the neural tube in the early vertebrate embryo? (1)

A

Directly underneath it (ventrally)

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19
Q

The notochord is classed as part of which germ layer in the early vertebrate embryo? (1)

A

Mesoderm

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20
Q

True or false? (1)

In the early vertebrate embryo, the whole of the eye is developed from the neuroectoderm.

A

False - the retina develops from the forebrain part of the neuroectoderm, but the lens develops from the surface ectoderm.

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21
Q

Describe briefly and simply how the eye is formed in the early vertebrate embryo. (4)

A
  • Optic vesicle (neuroectoderm) makes contact with ectoderm
  • Ectoderm invaginates to form lens placode
  • Placode keeps invaginating to form cup-like structure (lens vesicle)
  • Optic cup (neuroectoderm) and lens vesicle (ectoderm) develop into eye
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22
Q

Describe briefly and simply how the ear is formed in the early vertebrate embryo. (4)

A
  • Invagination of ectoderm to form otic placode
  • Formation of otic cup,
  • then otic vesicle.
  • Collection of cells breaks away from otic epithelium to form acoustic-vestibular ganglion
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23
Q

Describe what is meant by ‘the organiser’ when referring to early vertebrate embryos. (2)

A

The part of the embryo which can induce nearby cells

to become parts of the nervous system and other dorsal fates.

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24
Q

True or false? (1)

The organiser in an early vertebrate embryo is only able to cause neural induction - further determination and differentiation require further signalling.

A

True

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25
Q

True or false? (1)

In the early vertebrate embryo, the organiser is always located at the cranial end of the primitive streak.

A

False - in amphibians it is not

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26
Q

Name the organiser in an early chick embryo. (1)

A

Hensen’s node

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27
Q

Name the organiser in an early mammal embryo. (1)

A

Node

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28
Q

Name the organiser in the early amphibian embryo. (1)

A

Blastopore (dorsal) lip

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29
Q

True or false? (1)

The organiser (Hensen’s Node, etc) is the first part of the embryo to have its fate determined.

A

True

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30
Q

Describe the structure, location, and movement of the node/Hensen’s node during development of the early vertebrate embryo. (3)

A
  • Enlarged group of cells
  • Anterior end of primitive streak
  • Location of the node moves anteriorly then posteriorly as the primitive streak extends and retracts
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31
Q

Describe the cells which form the notochord, and how the node/Hensen’s node is involved in producing the notochord. (2)

A

The cells which migrate last during gastrulation form the notochord.

These cells migrate through the node.

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32
Q

Name two structures in the early vertebrate embryo which possess neural inducing activity. (2)

A
  • Notochord
  • (Hensen’s) Node
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33
Q

As well as signals produced by (Hensen’s) node in the early vertebrate embryo, describe the other requirement for neural induction. (1)

A

Ectoderm must have intrinsic competence (the ability to respond to signals).

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34
Q

Give the three criteria required for a molecule to be a signalling molecule and play a role in embryonic development. (3)

A
  • Necessary
  • Sufficient
  • Expressed at correct time
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35
Q

Describe simply how the notochord and node are able to induce neural competence in the early vertebrate embryo.

Name the molecules involved. (4)

A

Release of:

  • Follistatin
  • Noggin
  • Chordin
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36
Q

How do the molecules released by the notochord and node in the early vertebrate embryo help to induce neural fate? (1)

A

They are BMP antagonists

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37
Q

What is the role of bone morphogenic proteins (BMPs) in determining fate in the early vertebrate embryo? (1)

A

Promotes epidermal state, inhibits neural state

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38
Q

Describe the signalling pathway by which BMPs influence cell fate in the early vertebrate embryo. (4)

A
  • BMP binds to cell surface receptor
  • Triggers SMAD phosphorylation
  • SMAD activated
  • SMAD inhibits neural genes and activates epidermal genes
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39
Q

What types of molecules are BMPs in the early vertebrate embryo? (1)

A

Extracellular signalling molecules

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40
Q

What types of molecules are chordin, follistatin, and noggin in the early vertebrate embryo? (1)

A

Extracellular signalling molecules

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41
Q

What type of molecule is SMAD in the early vertebrate embryo? (1)

A

Transcription factor

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42
Q

Describe how FGF inhibits the BMP signalling pathway in the early vertebrate embryo. (3)

A
  • FGF binds to cell surface receptor
  • phosphorylation of smad
  • at a different site to that which is phosphorylated by BMP
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42
Q

Apart from BMPs and BMP antagonists, name another molecule which is required to confer neural competence in the early vertebrate embryo. (1)

A

FGF (fibroblast growth factor)

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42
Q

Give two roles of FGF in neural induction in the early vertebrate embryo. (2)

A
  • Sox3 expression
  • Inhibits BMP pathway
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43
Q

How is FGF produced in the early vertebrate embryo?

When in development does this occur? (2)

A

Expressed by (Hensen’s) node

later in development.

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44
Q

Name two Sox molecules which are important for neural induction in the early vertebrate embryo. (2)

A

Sox2

Sox3

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45
Q

What types of molecules are the Sox proteins? (1)

A

Transcription factors

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46
Q

Describe the expression of sox3 throughout development of the early vertebrate embryo. (2)

A

First expressed throughout ectoderm

before being restricted to neural ectoderm as tissue matures.

(also expressed in endoderm)

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47
Q

Describe the expression of sox2 throughout development of the early vertebrate embryo. (1)

A

Only expressed in neural ectoderm

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48
Q

When the nervous system starts to develop in the early vertebrate embryo, describe the expected distribution of sox2 in the AP axis. (1)

A

Expressed in anterior regions but not posterior regions
(anterior regions develop first)

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49
Q

Describe the order in which FGF and BMP are expressed during neural induction in the early vertebrate embryo. (2)

A

FGF expressed first to induce neural competence.

Then BMPs (and inhibitors) expressed to form neural or epidermal ectoderm.

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50
Q

Describe the gene/s expressed in the ectoderm of the early vertebrate embryo once it has been exposed to FGF. (1)

A

Sox3

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51
Q

What type of molecule is FGF in the early vertebrate embryo? (1)

A

Extracellular signalling molecule

52
Q

Give another name for the organiser in a fish embryo, which is found at the blastopore (dorsal) lip. (1)

A

The ship

53
Q

Which animal’s embryo is the closest model to a human embryo that we can use to study development? (1)

A

Mouse

54
Q

Describe one difference between mice embryos and other vertebrate embryos relating to the way that they fold in utero. (1)

A

Mouse embryos bend backwards but other embryos bend forwards.

55
Q

Describe what you would expect to happen if an area of mesoderm from the dorsal lip of the early amphibian embryo is transplanted to a different area of the organism. (2)

A
  • Initiates gastrulation and notochord formation
  • So the embryo develops two nervous systems
56
Q

Describe what you would expect to happen if the Hensen’s nodes from two donor quail embryos were taken and transplanted into a single chick embryo. (1)

A

Chick would develop 3 nervous systems.

57
Q

What would you expect to happen if a region of undifferentiated ectoderm was left to culture and the cells were…

a) left intact
b) dissociated
c) dissociated and added to BMP4

Explain why these things happen.

(6)

A

a) epidermis formed (intact cells express BMP so inhibit neural fates in each other)

b) Neural tissue formed (dissociated cells still express BMP but cells too far away to respond)

c) epidermis formed (cells inhibited by BMP)

58
Q

Describe where noggin would be expressed in an early chick embryo. (1)

A

Dorsal midline

59
Q

Describe where smad phosphorylation would occur in an early chick embryo. (1)

A

Outside CNS (so around the edge) of embryo

60
Q

foxi1 and gata2 are markers which indicate the epidermal fate in an early vertebrate embryo.

Describe the expected distribution/level of expression of these in a wild type zebrafish embryo.

How would this change if

a) BMP
b) noggin

are added? (3)

A
  • Outside of normal nervous system

a) larger area of expression

b) very little expression

61
Q

Describe the expected distribution/level of expression of sox2/3 in a wild type zebrafish embryo.

How would this change if

a) BMP
b) noggin

are added? (3)

A
  • Within nervous system

a) smaller area of expression

b) larger area of expression

62
Q

zic2b is a marker which is expressed in the anterior nervous system of the early vertebrate embryo.

Describe the expected distribution/level of expression of zic2b in a wild type zebrafish embryo.

How would this change if

a) BMP
b) noggin

are added? (3)

A
  • Mainly expressed in head of embryo

a) Smaller area of expression

b) Larger area of expression

63
Q

Complete the sentence. (2)

Overexpressing BMPs in the early vertebrate embryo results in the expansion of the ……………………. fate and repression of the ………………….. fate.

HINT: both answers are either neural or epidermal

A

epidermal

neural

64
Q

Complete the sentence. (2)

Overexpressing BMP antagonists in the early vertebrate embryo results in the expansion of the ……………………. fate and repression of the ………………….. fate.

HINT: both answers are either neural or epidermal

A

neural

epidermal

65
Q

Complete the sentence. (2)

Overexpressing the FGF signalling inhibitor, SU5402, in the early vertebrate embryo results in the expansion of the ……………………. fate and repression of the ………………….. fate.

HINT: both answers are either neural or epidermal

A

epidermal

neural

66
Q

How are chick embryos mainly used to research neural development, and why are they suited to this purpose? (2)

A

Transplantation of responding or signalling tissues.

They are generally larger and held in place (tethered on a membrane).

67
Q

How are zebrafish embryos mainly used to research neural development, and why are they suited to this purpose? (2)

A

Good for treatment with molecule injection (eg. RNA, antisense oligonucleotides, signalling molecules)

Zebrafish contain large cells in the early embryo, and as they divide the cells get smaller but the embryo doesn’t get any bigger, so anything which has been injected does not become diluted.

68
Q

Follistatin, chordin, and noggin all have orthologues in the invertebrate embryo.

What is it called? (1)

A

Sog

69
Q

Name the invertebrate orthologue of BMPs. (1)

A

DPP

70
Q

Name the invertebrate orthologue/s of SMAD. (1)

A

Mad/p-mad

71
Q

Give 2 similarities and 2 differences between neural induction in different vertebrate embryos. (4)

A

SIMILAR:
- Genes and signalling pathways (eg. sox2/3)
- All have an organiser which secretes BMP antagonists

DIFFERENT:
- Different name for the organiser
- In some (fish, amphibians) the organiser is static whereas others (birds, mammals) it moves with the primitive streak

72
Q

Complete the sentence. (1)

When it is first formed, the neural tube is a …………………. epithelium of proliferating cells.

A

Pseudostratified

73
Q

Why does the neural tube in the early vertebrate embryo appear as a pseudostratified epithelium? (1)

A

Due to cytokinetic movements during the cell cycle.

74
Q

Describe the cytokinetic movements of cells in the neural tube of the early vertebrate embryo during the cell cycle. (3)

A
  • Nucleus and cytoplasm moves up (away from lumen of neural tube)
  • Then they move downwards towards lumen
  • Then retract processes and divide

(connections of processes are reestablished by daughter cells)

75
Q

True or false? (1)

In the developing neural tube, a cell which is proliferating cannot differentiate, and a cell which is differentiating can no longer divide.

A

True

76
Q

Describe in general, where cells of the neural tube move to once they stop dividing and start differentiating. (1)

A

Cells move outwards from proliferating epithelium and further away from lumen of neural tube.

77
Q

Describe the specific migration of differentiating cells in the spinal cord region of the neural tube.

(Older cells vs newer cells, name the gradient).

(3)

A

Newly born cells push existing cells up and sit under them.

Oldest cells on outside, newest cells on inside.

Outside-in gradient

78
Q

Describe the specific migration of differentiating cells in the cortex region of the neural tube.

(Older cells vs newer cells, name the gradient).

(3)

A

Newly born cells climb through the layers of existing cells and sit on top of them.

Newest cells on outside, oldest cells on inside

Inside-out gradient

79
Q

How do differentiating cells in cortex part of the neural tube climb through layers of existing cells to sit on top of them? (1)

A

Use the architecture of radial glial cells.

80
Q

Describe why it is important to have a precise balance between cell proliferation and cell differentiation in the neural tube of the early vertebrate embryo. (2)

A
  • If all cells started differentiating the CNS would no longer grow
  • If all cells continued to proliferate there would be no differentiation
81
Q

True or false? (1)

In the neural tube of the early vertebrate embryo, cellular differentiation only starts to occur once all cells have stopped dividing.

A

False - mature cells are gradually produced while other cells continue dividing and proliferating

82
Q

Describe the change in gene expression throughout the AP axis of the early vertebrate embryo as some neural tube cells begin to stop dividing and differentiate. (2)

A
  • Change from producing FGF8 to Raldh2
  • Anterior part starts producing Raldh2 first, while the posterior part continues producing FGF
83
Q

Describe the role of FGF8 in balancing cell division and differentiation in the early vertebrate embryo. (2)

A

FGF inhibits Pax6

Which is necessary for neural differentiation.

(FGF inhibits differentiation)

84
Q

Which part of the early vertebrate embryo produces FGF8 as it plays a role in promoting cellular proliferation in the neural tube? (1)

A

Presomitic/paraxial mesoderm

85
Q

What is the role of Raldh2 in the early vertebrate embryo? (2)

A

Produces retinoic acid

to promote cellular differentiation.

86
Q

Name the part of the early vertebrate embryo which produces Raldh2 to promote cellular differentiation in the neural tube. (1)

A

Somitic mesoderm

87
Q

Describe where in the cells of the early vertebrate embryo neural tube the receptors for retinoic acid are located. (1)

A

In cytoplasm

88
Q

Describe how FGF8 and retinoic acid interact with each other in the early vertebrate embryo to regulate the balance between proliferation and differentiation in the neural tube. (1)

A

They show mutual inhibition

89
Q

True or false? (1)

As retinoic acid acts on cells in the neural tube of the early vertebrate embryo, these cells immediately begin to differentiate and stop proliferating.

A

False - retinoic acid gives the cells the ability to differentiate, but not all cells go on to differentiate straight away

90
Q

Describe the process by which the mesoderm of the early vertebrate embryo switches from producing FGF8 to inhibit cell differentiation to producing Raldh2 to promote cell differentiation. How is a gradient of cell differentiation established in the embryo? (2)

A

Mesoderm starts to form somites

from anterior to posterior.

91
Q

Give four genes expressed in early neuroblasts in the vertebrate neural tube.

Name an additional two which are expressed as these cells begin to differentiate. (6)

A
  • Sox2
  • Sox3
  • Notch
  • HES-1
  • Delta
  • Sox4/11
92
Q

In areas of the early vertebrate embryo neural tube where cells are exposed to retinoic acid, the cells are told to stop dividing and start differentiating. However if all cells stopped dividing right away, the nervous system would no longer be able to expand.

Describe how some cells are able to ‘ignore’ this signal and continue proliferating for a while. (1)

A

Inhibition by notch-delta

93
Q

Describe the pathway by which cells stop proliferating and start differentiating in the early vertebrate embryo when signalled by retinoic acid. (3)

A
  • Transcription of neurogenin
  • Neurogenin protein activates NeuroD transcription
  • NeuroD protein promotes neural differentiation
94
Q

Describe how notch-delta signalling in the neural tube of the early vertebrate embryo prevents a subset of cells from differentiating.
How does it affect the normal pathway leading to neural differentiation? (4)

A
  • Delta binds to notch
  • Notch intracellular domain is cleaved (and travels to nucleus)
  • Notch activates transcription of HES genes
  • HES is a transcriptional repressor - stops Neurogenin transcription

(Neurogenin cannot activate NeuroD to activate differentiation)

95
Q

Describe how the process of lateral inhibition and the expression of delta is able to regulate the balance between cellular proliferation and differentiation in the neural tube of the early vertebrate embryo. (4)

A
  • As cells start differentiating they express delta
  • Delta provides lateral inhibition of differentiation to neighbours in three dimensions
  • Neighbours will continue to proliferate
  • Once a cell differentiates and migrates away the inhibition is removed so a new cell can then begin to differentiate
96
Q

As a differentiating cell migrates away from the neural tube in the early vertebrate embryo, lateral inhibition is removed from neighbouring cells and one is then able to begin differentiating itself.

How does the embryo decide which cell should be next to differentiate? (2)

A
  • The next cell to reach the right stage in the cell cycle
  • and which expresses delta to inhibit neighbours, but is not inhibited itself

will be next to differentiate

97
Q

Complete the sentence. (1)

In an experiment where researchers are overexpressing HES-1 to test its role in inhibiting neural differentiation in the early vertebrate embryo, they are testing the …………………. of HES-1 to cause an effect. This is a ……………………. of function experiment.

HINT: answer is either sufficiency or necessity, then either gain or loss

A

Sufficiency

Gain

98
Q

Name a technique which could be used to promote overexpression of HES-1 is embryonic mouse retina and forebrain cells. (1)

A

Viral vector

99
Q

Describe the expected results of an experiment in which neural tube cells in the early vertebrate embryo are manipulated to overexpress HES-1. (2)

A
  • Cells remain in ventricular zone of neural tube and divide
  • However they can’t migrate and differentiate, so eventually die
100
Q

Complete the sentence. (1)

In an experiment where researchers are knocking out HES-1 to test its role in inhibiting neural differentiation in the early vertebrate embryo, they are testing the …………………. of HES-1 to cause an effect. This is a ……………………. of function experiment.

HINT: answer is either sufficiency or necessity, then either gain or loss

A

Necessity

Loss

101
Q

Describe what you would expect to see in an experiment where HES-1 is knocked out in the forebrain of the early vertebrate embryo. (2)

A
  • Premature differentiation
  • Proliferation ceases so organism has small/underdeveloped forebrain
102
Q

In experiments where HES-1 is knocked out in the early vertebrate embryo to test its role in inhibiting neural tube cell differentiation, the ‘expected’ results are only seen in the forebrain regions.

Why is this? (2)

A
  • In other areas of the embryo, additional forms of HES are present which will take over and inhibit differentiation
  • However only HES-1 is present in the forebrain
103
Q

Complete the sentence. (1)

In an experiment where researchers are overexpressing delta to test its role in inhibiting neural differentiation in the early vertebrate embryo, they are testing the …………………. of delta to cause an effect. This is a ……………………. of function experiment.

HINT: answer is either sufficiency or necessity, then either gain or loss

A

Sufficiency

Gain

104
Q

Name a technique which could be used to promote overexpression of delta in embryonic chick retina cells. (1)

A

Viral vector

105
Q

Describe the results you would expect to see in an experiment where delta is overexpressed in neural tube cells of the early vertebrate embryo. (1)

A
  • Inhibition of differentiation and migration
106
Q

Complete the sentence. (1)

In an experiment where researchers are overexpressing a faulty form of delta to test its role in inhibiting neural differentiation in the early vertebrate embryo, they are testing the …………………. of delta to cause an effect. This is a ……………………. of function experiment.

HINT: answer is either sufficiency or necessity, then either gain or loss

A

Necessity

Loss

107
Q

Dominant-negative delta lacks the delta intracellular domain.
Describe how expressing this faulty delta in cells is able to cause loss of function of the notch-delta signalling pathway. (3)

A
  • Faulty delta binds to notch
  • but does not produce a response.
  • Faulty delta stops functional delta from binding.
108
Q

In experiments investigating the differentiation and migration of cells in the neural tube of the early vertebrate embryo, name two markers that can be used to identify differentiating neurones. (2)

A

Islet 1/2

Neurofilament

109
Q

Describe the expected results in an experiment where dominant-negative (faulty) delta is expressed in neural tube cells of the early vertebrate embryo. (1)

A

Premature differentiation (cessation of proliferation)

110
Q

Describe what BrdU is, and how it can show proliferating or non-proliferating cells in the early vertebrate embryo. (2)

A

BrdU is a marked nucleotide (thymidine analogue) which gets incorporated into DNA during DNA synthesis.

If the label is expressed in a cell, it means that the cell is proliferating (and synthesising new DNA molecules to incorporate BrdU).

111
Q

Briefly describe an experiment which can be performed in the developing embryo which can help to determine whether a cell’s fate is determined before or after its birth date.

What results would you expect to see for both options? (4)

A
  • Label one proliferating precursor cell
  • Look at offspring (cells containing label) to see what cells have been produced
  • If cell fate is determined before birthdate, offspring cells will be identical
  • If cell fate is determined after birthdate, offspring cells will be varied
112
Q

How are proliferating cells labelled in the early vertebrate embryo when carrying out an experiment to determine whether cells acquire their fate before or after their birth date? (1)

A

Virus + beta-galactosidase

113
Q

Describe whether neural progenitor cells in the retina of the early vertebrate embryo produce identical or different offspring.

What does this mean regarding whether cells acquire their fate before or after their birth date? (2)

A

Different offspring

So cells acquire fate after birth date

114
Q

Describe whether neural progenitor cells in the forebrain of the early vertebrate embryo produce identical or different offspring.

What does this mean regarding whether cells acquire their fate before or after their birth date? (2)

A

Identical offspring

Cells may have fate decided before birth date (while still dividing)

115
Q

Define what we mean by a cell’s ‘birth date’ in the early vertebrate embryo. (1)

A

A cell’s birth date is the day when in stops dividing and starts differentiating.

115
Q

When talking about cells in the early vertebrate embryo acquiring their fate before or after their birth date, in what axis are we referring to cell fate? (1)

A

Medial-lateral axis

116
Q

Describe a method which could be used to study cell birth dates in a vertebrate embryo, and explain how it works. (6)

A
  • Label cells with 3H-Thy or BrdU
  • These marked nucleotides only get incorporated into cells making DNA and dividing
  • Wash out label after giving it time to be incorporated
  • When looking in the future, cells born on the day that the label was injected will still show the label
  • Cells which were born before label injected do not show label as it was never incorporated into the cell as it was not dividing
  • Cells born after label was injected do not show label as multiple divisions have taken place since injection and diluted label
117
Q

Describe a way of labelling cells in the entire embryo (not just specific cells) in…

a) frog embryo
b) mammalian embryo

(2)

A

Frog - add label to water

Mammal - inject label into mother

118
Q

True or false? (1)

When labelling cells in the early vertebrate embryo to study their birth dates, the label which was injected will still be seen long into the future in cells born on the same day.

A

True - because cells born on the day that the label was injected stop dividing after incorporating the label, the label is not diluted, and remains in the cells long into the future

119
Q

Describe to what extent a cell’s fate is determined in the medial-lateral axis according to birth date. (1)

A

Determines what layer of cortex the cell will end up in

120
Q

When carrying out an experiment to label cells in the early vertebrate embryo and determine their birth dates and fates, why isn’t the label present in any cells if the label was injected during very early stages of gestation? (2)

A

All cells are still dividing (none are being born yet)

so label gets diluted and undetectable in all cells.

121
Q

When carrying out an experiment to label cells in the early vertebrate embryo and determine their birth dates and fates, why isn’t the label present in any cells if the label was injected during very late stages of gestation? (2)

A

Cells are no longer dividing

so they do not incorporate the stain in the first place.

122
Q

Describe the position/location of cells in the early vertebrate embryo which were labelled with BrdU and have retained that stain, as cells are just beginning to stop dividing and differentiate. (1)

A

They will be in layer 6 of the cortex

123
Q

Describe the position/location of cells in the early vertebrate embryo which were labelled with BrdU and have retained that stain, as cells are ending their phase of differentiation in the neural tube. (1)

A

Layer 1 of the cortex

124
Q

Do cells migrate according to fate, or is cell fate determined by environment in the vertebrate embryo?

(in the medial-lateral axis, ie. layers of the cortex)

A

Cells migrate according to fate

(once cells stop dividing they ‘know’ what cells they are, and then migrate to the right layer)

125
Q

A study was carried out where a cell which is just starting to cease proliferation and begin differentiation/migration on embryonic day 9 is transplanted into an embryo at postnatal day 1.

Normally, the E29 cell will migrate to layer 6, and P1 cells would migrate to layer 2/3.

To which layer would the E29 cell migrate to in the P1 embryo if it is transplanted after it has completed its last S phase of cell division? (1)

A

Layer 6 (cell retains fate)

126
Q

A study was carried out where a cell which is just starting to cease proliferation and begin differentiation/migration on embryonic day 9 is transplanted into an embryo at postnatal day 1.

Normally, the E29 cell will migrate to layer 6, and P1 cells would migrate to layer 2/3.

To which layer would the E29 cell migrate to in the P1 embryo if it is transplanted as it is completing its last S phase of cell division? (1)

A

Layer 2/3 (cell takes on fate of new embryo)

127
Q

What is the S phase of cell division? (1)

A

DNA synthesis

128
Q

When exactly during a cell’s last cell cycle does it acquire its fate on it’s birth date in the vertebrate embryo? (1)

A

After last S phase (DNA synthesis) but just before it migrates.

129
Q

Describe the hypothesis which describes how a cell which is still proliferating but getting ready to migrate from the neural tube in the vertebrate embryo knows what layer of the cortex it is going to become. (1)

A

Newly-differentiating and migrating cells send signals back to still-proliferating cells to indicate their fate and therefore the fates of the next cells to migrate.

Neuroscience Y2S1 (16 decks)

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