Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Module Assessment 6 > MA 6 > Flashcards

MA 6 Flashcards

1
Q

What makes Xenopus a good model organism

A

-large eggs with defined animal and vegetal halves that are suitable for transplantation experiments
-easily microinjected, making them good for genetic studies
-used to study gastrulation by removing and transplanting tissues
-high fecundity- lots of eggs in each clutch
-external fertilization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Cortical Rotation

A
  • outer part of the embryo rotates while the inner part of the egg remains in place (molecules inside move relative to one another)
    -reveals the grey crescent
    -location of the grey crescent is defined by the point of sperm entry
    -grey crescent is on the dorsal side of the embryo
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Experiment: expose embryos to UV light

A
  • prevents cortical rotation.
    -greater amounts of UV light decrease the amount of cortical rotation
    -anterior structures are missing
    -embryo becomes ventralized, no more dorsal structures. This means that cortical rotation is necessary for localizing dorsalizers.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does cortical rotation occur?

A

-sperm centriole enters the egg upon fertilization
- this allows the MTs to become organized.
-MT tracks separate the outside of the embryo from the inside, then provide a track for the cortical cytoplasm to rotate on.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

cleavage in amphibians

A

-Unequal radial holoblastic cleavage
-first cleavage is partway through the embryo
-second cleavage begins while the first one is happening
-additional cleavages in the animal pole compared to the vegetal pole, this is because the vegetal cells have a lot of yolk which makes it harder for them to divide. vegetal pole has larger cells as a result

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

As a result of cleavage…

A
  • 6000 cells
  • No volume change
  • No growth of individual cells- embryo is focused on mitosis
    -more membrane throughout the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Blastocoel

A

-space for cells to move through during gastrualtion
-divides the animal and vegetal cells into two distinct populations. This prevents interactions and allows the two populations to have unique characteristics.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

experiment: centrifugation of embryos

A
  • increases the amount of cortical rotation
    -induces a second axis
    -embryos have two heads
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

morula

A
  • embryo is 16-64 cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

blastula

A
  • embryo is 128 cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Mid Blastula Transition

A

-cell divides enough so that there is a certain amount of DNA. Protein gets titered by DNA, and this induces the MBT.
-shift from using maternal stored mRNA to zygotic DNA
-mitosis slows down
-new genes are being transcribed
-cells become different from one another based on location and signaling molecules.
-cleavages become asynchronous
-cells become motile and start moving around

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

experiment: treatment with Actinomycin

A

-actinomycin blocks transcription of mRNAs
-boost in proteins from the translation of maternal mRNAs still occurs.
-but, translation of zygotic genome does not happen
-less protein in treatment group than control once the MBT happens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Goal of gastrulation

A

-get the germ layers into positions that will mimic their final functions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the site of gastrulation in xenopus

A

-dorsal lip of the blastopore
-location is determined by the site of fertilization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are some early events of gastrulation

A

-cells begin to roll in to the embryo
-dorsal lip becomes bigger and extends around the embryo
-yolky endodermal cells get sucked into the embryo
-outside cells become ectoderm
-neural plate forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

fate of vegetal cells

A

endoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

fate of animal cells

A

ectoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

cells opposite the site of sperm entry/ the Spemann organizer become…

A
  • neural ectoderm
    -notochord mesoderm
    -head endoderm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

cells beneath the blastocoel become…

A

mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

overview of gastrulation

A
  • cells move, forming the gut
    -begins at the dorsal lip of the blastopore
    -neurula folds up forming the neural tube
    -defines the A/P axis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

5 Key movements during gastrulation

A

-epiboly
-vegetal rotation
-invagination
-involution and migration
-convergent extension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

epiboly

A

thinning and spreading of the animal cap cells over the vegetal hemisphere
-powered by proliferation and radial intercalation
-cells on the outside compress forming a thinner layer of cells
-amount of the embryo covered increases
-ectodermal cells move down, around and into the lip

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

vegetal rotation

A

vegetal cell asymmetrically press up against the inner blastocoel roof on the dorsal side
- vegetal cells migrate and crawl along the blastocoel.
-these tissues give rise to the gut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Bottle cell formation and ingavination

A

localized apical constriction at the dorsal blastopore lip creates anisotropic forces that foster invagination
- bottle cells form as a result of apical constriction
-forms the dorsal lip of the blastopore

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

involution and migration

A

tissues roll in and pulls along the future mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

convergent extension

A

medial to lateral intercalation of cells on the midline that drivers anterior to posterior extension

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Steps of gastrualtion

A
  1. Bottle cells initiate invagination
  2. Dorsal lip forms, cells start to pull in
  3. Mesoderm moves along the roof of the bastocoel, epiboly of ectoderm wraps cell around while other tissues move in. Blastocoel gets displaced by the developing archenteron. ventral lip of the blastopore gets displaced by the developing archenteron
  4. tissues move all the way across the embryo. Blastocoel gets smaller as the archenteron gets larger, Blastocoel gets displaced to the opposite side of the dorsal lip.
  5. tissues move completely around
  6. some of the mesoderm moves around forming various organs. A/P axis is fully defined.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

collective cell migration

A

-multiple rows of cells follow one another in a cluster
-leading row pushes out lamellipodia that connects to fibronectin lining the roof of the blastocoel
-b-catenin is essential for keeping the cluster of cells together
-integrins facilitate binding between cells and the ECM
-tension allows for the pulling of cells and creates a gap between the cells and the roof of the blastocoel.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

experiment: KO E-cadherin in the embryo

A

-maternal messages in the embryo are knocked out
-no cadherins means that cells no longer connect to one another
- no organization of cells or formation of the blastocoel
-gastrulation does not occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

experiment: inject the cell with the cell binding portion of fibronectin

A
  • integrin binding sites become saturated
    -improper binding
    -gastrulation is not able to occur and the ectoderm gets stuck on the outside of the embryo.
    -cells are non involuted
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

yolk plug

A

remaining patch of endoderm
-at this point: all endodermal precursors have been brought into the interior of the embryo
-ectoderm envelopes the surface
-mesoderm is between the two layers
-gastrulation is mostly complete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

mesoderm layer becomes…

A

notochord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

IMZ

A

involuting marginal zone.
-undergoes convergent extension
-both ends extend at the same time
-helps induce the A/P axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what are the two functions of the vegetal cells

A

A. differentiate into endoderm
b. induce cells immediately above them to become mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Axis formation in xenopus

A

-maternal VegT mRNA gets translated
-VegT turns on Nodal
-Nodal activates Eomes
-Eomes is a TF that tells these cells to become mesoderm
-Eomes and Nodal turns on VegT in a positive feedbalc loop
-Veg1 turns on Wnt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Sox17

A

-induce endodermal cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Vg1

A

dorsal mesoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

VgT

A

mesoderm and endoderm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

migration and involution of the mesoderm induces…

A

-Establishment of the AP axis
-induces formation of the neural tissue and the forebrain
-induces tissue to become posterior brain structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

primary embryonic induction

A

first set of inductive events that happens in the developing embryo
-induction where the progeny of dorsal lip cells induce the dorsal axis and neural tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

experiment: VgT KO

A

entire embryo becomes epidermis, dorsalizers are no longer there to induce dorsal phenotypes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Spemann’s experiment: nuclear equivalence

A

-Use of a baby hair to separate out one nucleus from the rest
-development proceeds normally but one newt is smaller than the other
-each nucleus has enough information to encode an entirely functional embryo (conditional specification)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

grey crescent

A

gives rise to cells that initiate gastrulation. Crucial for development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

experiments: first cleavage does not bisect the grey crescent

A
  • one embryo, containing the grey crescent develops normally. it has all of the elements needed to induce dorsal structures
    -the other embryo does not contain the grey crescent, this one is completely epidermis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

experiments: Spemanns transplantation experiments

A

-early cells express conditional development. Later, gastrula cells exhibit autonomous development
-transplanting tissue in early gastrula, tissue is conditionally specified
-presumptive neural tissue becomes epidermis
-transplanting later, tissue becomes what it is autonomously specified to be
-presumptive neural tissue becomes neural tissue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is the first tissue to become autonomously specified

A

Spemann organizer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Spemann Organizer

A

-only part of the embryo that forms a second axis when transplanted
-Above the dorsal lip of the blastopore and derived from the grey crescent
-contains mesoderm layers that later form somites
-induces formation of neural and dorsal tissues
-organizes D/V and A/P axis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Experiment: transplantation of the Spemann Organizer

A

-transplanted into an embryo in early gastruation
-induces a second site of gastrulation
-second set of neural tube, lumen of the gut, notochord resulting in two conjoined embryos

49
Q

Niewkoop Center

A

dorsalmost vegetal cells that are capable of inducing the Spemann organizer
-b-catenin is a key signaling molecule in determining where this is
-necesary and sufficient in forming the D/V axis

50
Q

where is b-catenin localized

A

dorsal side of the embryo

51
Q

How does b-catenin localize

A

A. Formation of parallel arrays of MTs extend along the vegetal hemisphere along the future D/V axi
b. cortical rotation
C. Dsh becomes localized at the dorsal position of the embryo- it gets placed there by being transported by kinesin (moves towards the positive end of the MTs)
-before fertilization, b-catenin is found all throughout the embryo

52
Q

b-catenin induces the A/P axis by…

A

initiating the movement of the involuting mesoderm

53
Q

Dsh and GP

A

initiate the inactivation of GSK3 and the protection of b-catenin

54
Q

Wnt11

A

Amplifies the signal and stabilizes the GbP and Dsh and organizes them to protect b-catenin

55
Q

b-catenin

A

associates with other TFs and gives them new properties

56
Q

GSK3

A

phosphorylates b-catenin and targets it for degredation by the proteosome of the ventral side
GSK3

57
Q

GSK3 is inactivated by…

A

Dsh, GbP and Wnt11

58
Q

experiment: inject a broken GSK3

A

-no more degredation of b-catenin
-b-catenin is present all throughout the embryo
-induces the formation of a second axis

59
Q

b-catenin is also used for

A

-ovary induction
-induction of the micromeres during gastrulation
-axis formation in xenopus

60
Q

High levels of Nodal and b-catenin…

A

induce the organizer

61
Q

High levels of nodal and low levels of b-catenin…

A

ventral mesoderm

62
Q

nodal is upregulated by…

A

overlap of b-catenin and vg1

63
Q

when is b-catenin upregulated?

A

up until gastrulation- localized in both the niewkoop center and the Spemann organizer

64
Q

What does the organizer do?

A

a. self differentiates into mesoderm
b. dorsalizers surrounding mesoderm form somite cells
c.dorsalizes ectoderm and induces the formation of the neural tube
d. initiates the movements of gastrulation

65
Q

How does the organizer do its job?

A

-no positive inducer for neural tissue
-neural tissues form by blocking the molecules that induce formation of the epidermis
-neural tube is the default. Forms when protected from bMP molecules.

66
Q

bmp

A

powerful ventralizer, induces the formation of the ectoderm as well as dorsal mesoderm.

67
Q

experiment: KO bmp

A

only neural tissue forms, many small heads

68
Q

noggin

A

-one of the genes found in a mutant screen.
-dorsalizes an embryo that is ventralized by UV light
-too much noggin forms an embryo that is completely dorsal
-antagonizes bMP4 and bMP2 and allows for the induction of neural tissued

69
Q

chordin

A

binds to bmp4 and bmp2 and prevents complexing with their receptors

70
Q

Follistatin

A

inhibits bmps

71
Q

when does neurulation begin?

A

during gastrulation

72
Q

what three groups does the ectoderm differentiate into

A

A. outer ectoderm
b. neural crest cells
C. neural tube

73
Q

outer ectoderm becomes…

A

mostly epidermis

74
Q

neural crest cells become…

A

-mesenchymal cells, neurons pigment, facial cartilage

75
Q

neural tube becomes…

A

brain and CNS

76
Q

convergent extension in neurulation

A

convergent extension allows for elongation of the embryo. This occurs in a defined direction

77
Q

primary neurulation

A
  • cells surrounding the neural plate direct it to proliferate, invaginate, and separate from the ectoderm, forming a hallow tube
  • notochord directs the overlying ectoderm to form the neural tube
    -creates the neural tube and neural crest and leaves behind the epidermis
78
Q

Steps of neruation

A
  1. elongation/ folding of the neural plate
    -neural plate is created from elongated dorsal ectodermal cells
    -cells begin to fold upward forming the MHP and neural groove
  2. Convergence of folds and formation of the DLHPs
    -epidermal cells have a pushing force that push cells towards the midline
    -wedges, apical constriction helps with bending
  3. Closure: cells at dorsal most portion of the neural tube become neural crest cells
    -separation due to different kinds of cadherins
    -n-cadherins in neural cells
    -e-cadherins in epithelium
    -cell cell interactions and microfilaments are crucial for neurulation
79
Q

secondary neurulation

A

neural tube forms a solid chord of cells that sinks into the embryo

80
Q

neural tube closure in mammals

A

multiple points of closure in humans rather than one point of closure

81
Q

spina bifida

A

failure of the end of the neural tube to close

82
Q

anacephaly

A

anterior of the neural tube does not close
-brain is exposed to amniotic fluid and degrades

83
Q

minor issues in closure 3

A

cleft lip/cleft pallette

84
Q

environmental impacts on NTD

A

folic acid is added to bread and prenatal vitamins because low folate levels cause epigenetic changes and mutations that cause neural tube defects

85
Q

mammalian eggs

A

-smallest in the animal kingdom, difficult to manipulate experimentally
-hard to visualize
-produced in smaller numbers
-mouse eggs mostly used in experiments

86
Q

steps of fertilization in mammals

A

-early follicles have stored eggs that are arrested in meiosis
-hormones stimulate the release of the egg into the fallopian tube- fimbrae facilitate this movement
-eggs begin to accumulate stored mRNAs and nutrients
- egg moves down the fallopian tube, this is where fertilization occurs.
- fertilization allows the egg to complete meiosis
-cleavage begins as the embryo moves down the fallopian tube and into the uterus
- egg hatches from zona pellucida and implants into the uterus

87
Q

zona pellucida

A

outer membrane that prevents the egg from hatching prematurely
-premature hatching results in ectopic pregnancy, or implantation into the uterus and can be life-threatening if left untreated

88
Q

Cleavage in mammals

A

-rotational holoblastic
-first cleavage is meridional
-second cleavage has one meridional plane and one equatorial plane
- cleavages go all the way through the embryo

89
Q

how is mammalian cleavage different from other model organism we’ve studied?

A

-asynchronous cell divisions start early, so the embryo can have an odd number of cells at any point
-mammalian zygotic genome becomes active earlier- it is needed during cleavage and gastrulation
-less reliance on stored maternal mRNAs
-some of the slowest cleavages in the animal kingdom

90
Q

totipotent

A

cells are capable of producing any cell type - seen in early cells`

91
Q

pluripotent cells

A

cells that can form many types of cells
-we see this in the ICM, these cells can form many types of cells, but cannot differentiate into trophoblast

92
Q

early 8 cell stage

A

cells are loosely arranged

93
Q

compacted 8 cell stage

A

-E-cadherins are expressed
-tight junctions begin to form
-embryo becomes compacted
- inside of the sphere is not sealed off, but gap junctions allow small molecules to pass through

94
Q

16 cell stage

A

-morula
-cells split between the inside and the outside and begin to develop unique characteristics based on where they are positioned
-no internal cavity yet

95
Q

blastocyst

A

-cavitation- the blastocoel forms
-outer trophectoderm and ICM form

96
Q

trophectoderm

A

these cells become extraembryonic tissues that are critical for supporting the growth of the embryo
-chorion/ fetal portion of the placenta
-has integrins that allow attachment to the wall of the uterus
-proteases that are able to degrade the uterine lining and allow for implantation

97
Q

Inner Cell Mass (ICM)

A

cells that become the embryo, yolk sac, allantois, and the amnion
-also supports the trophoblast by secreting cells that help it divide

98
Q

Overview of implantation

A
  1. Hypoblast cells delaminate from the ICM and line the boastocoel
  2. loss of membranes, syncytium forms, trophoblast forms villi (cyto and syncytial trophoblast and ingression into uterine tissue
  3. amniotic cavity is filled with amniotic fluid and surrounds the embryo
    epiblast separates into embryonic epiblast and amniotic ectoderm
  4. yolk sac forms from the hypoblast and the blood vessels begin to provide the embryo with nutrients from the mother
99
Q

syncytial trophectoderm

A

placental barrier between maternal and fetal blood that allows for exchange of nutrients and gasses
-facilitates in implantation by production of enzymes and apoptotic factors

100
Q

cytotrophectoderm

A

-internal of the syncytiotrophoblast and external to the blastocyst.
-breaks down the endometrial cells and allows finger like projections to penetrate through and pull the embryo until it is completely covered

101
Q

epiblast

A

pluripotent primary lineage that will form the definitive germ layers of the embryo

102
Q

embryonic epiblast

A

single celled epithelium which generates the embryo through gastrulation

103
Q

amniotic ectoderm

A

epithelial layer that lines the inner roof of the amniotic cavity. derived from the epiblast before gastrulation begins

104
Q

yolk sac

A

not used by humans but remains due to shared ancestry with avians

105
Q

somites

A

segmental axial structures of vertebrate embryos that give rise to vertebral column, ribs, skeletal muscles, and subcutaneous tissues

106
Q

gastrulation in mammals

A

-initiated at the SMO - implantation of the SMO can induce gastrulation in other tissued
-forms the primitive streak and the primitive groove
-cells move into the groove and down into the deeper layers of the embryo
-hypoblast cells get displaced by the epiblast cells
-hypoblast cell eventually form the endoderm
-EMT occurs as the cells begin to move around
-cells between the two layers move around

107
Q

what happens of the SMO is duplicated

A

conjoined twins- the point at which they are conjoined depends on the site of the duplication

108
Q

formation of the notochord

A

mesodermal cells form tight connections with the overlying mesoderm. This anchors the folding neural tube
-formation of the neural tube is initiated by the movement of the dorsal mesoderm and signaling of dorsalizers that repress the formation of epidermal ectoderm

109
Q

What are the 3 responsibilities of the vertebrate ectoderm

A
  1. become the neural plate
  2. become the epidermis
  3. become the neural crest, forming the peripheral nervous system
110
Q

Development of the placenta

A

blood from the mother can now be released into the placental space, allowing for the exchange of nutrients and oxygenated/ deoxygenated blood.
-formed from the chorion, the trophoblast and blood vessel containing mesoderm

111
Q

choronic villi

A

-contains capillary beds from the baby
-connects the blood supply from the fetus to the mother
-exchange of deoxygenated blood and waste

112
Q

monozygotic twins

A

come from one egg

113
Q

twins- less than 5 days

A

-each embryo has its own blastocyst and trophoblast
-this causes the development of two chorions and two amnions

114
Q

twins- days 5-9

A

blastocyst is formed already,
-one trophectoderm between two babies, but 2 ICMs
-this leads to the development of 2 amnion within one chorion

115
Q

twins- after day 9

A

-one amnion and one chorion
-concern for conjoined twins because conjoined twins are normally formed during gastrulation

116
Q

dizygotic twins

A

2 eggs, the mother ovulates two eggs instead of one, and both get fertilized

117
Q

chorion

A

extraembryonic membrane and the portion of the placenta that enables the fetus to get oxygen and nourishment from the mother. Also secretes hormones that cause the mother’s uterus to retain the fetus and produces regulators of the immune response so that the mother will not reject the embryo

118
Q

amnion

A

thin membrane forming a closed sac about the embryo that contains fluid that protects it from shock or drying out

119
Q

allantois

A

fetal membrane lying below the chorion in many vertebrates. Part of the placenta in mammals

Module Assessment 6 (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions