Test 3 Flashcards
(322 cards)
1
Q
As a zygote, the organism:
A
- Consists of one cell of only one type
- Consists of unrealized genomic potential
- Operates using stored materials
- Has “relationships” with no other cells
- Is relatively homogeneus
2
Q
True or false, the zygote is polarized to some degree
A
True
3
Q
What does early development involve
A
- Development of new “raw materials” for building embryo
- Establishing new relationships between numerous cells
- Further polarizing the organism
4
Q
Steps of early development
A
- Cleavage
- Establishment of cell fate
- Establishment of body axes
- Gastrulation
5
Q
Cleavage
A
- Cell cycle control
- Rapid cell divisions, division of fertilized egg into many cells
6
Q
Establishment of cell fate
A
Specification
7
Q
Establishment of body axes
A
(anterior posterior, dorsal ventral, left right)
8
Q
Gastrulation
A
Cells undergo displacement, cells move to different parts of the embryo, cells aquire new neighbors
9
Q
How are cell fates specified during cleavage
A
Cell to cell interactions and asymmetric distribution of morphogenic determinants
10
Q
What initially controls cleavage
A
Factors stored in the egg
11
Q
Factors stored in the egg
A
Stored proteins, mRNAs
12
Q
Mitosis promoting factor
A
Stimulates the cell cycle (initiates cell division during mitosis and meiosis)
13
Q
Where does MPF come from
A
Mother
14
Q
What stops division
A
Absence of MPF
15
Q
Cyclin B
A
Controls cdc2 activity
16
Q
cdc2
A
Cyclin-dependent kinase
17
Q
CDK
A
Phosphorylates histones
18
Q
What happens when cyclin B degrades
A
Cell division stops
19
Q
What controls the cyclin B presence and degradation
A
Egg cytoplasmic proteins
20
Q
What happens when the maternal stores are used up
A
Embryonic control of the cell cycle
21
Q
Mid Blastula Transition
A
Must produce its own proteins
22
Q
Post MBT
A
- Cell cycle adds two new G phases
- New mRNA transcription
- Cell division becomes asynchronous
23
Q
How does the cell cycle of blastomeres compare with that of somatic cells
A
Cycle is like somatic cells after MBT
24
Q
Karyokinesis
A
Mitotic division of cells nucleus
25
Cytokinesis
Division of cytoplasm plus organelles
26
Mechanical agent of karyokinesis
Mitotic spindle
27
Mechanical agent of cytokinesis
Contractile ring
28
Major protein composition of karyokinesis
Tubulin microtubules
29
Major protein composition of cytokinesis
Actin microfilaments
30
Location of karyokinesis
Central cytoplasm
31
Location of cytokinesis
Cortical cytoplasm
32
Positioning of mitotic spindle and contractile ring relative to eachother
Perpendicular
33
What affects how cleavage occurs
Position of centrioles and yolk
34
Types of cleavage
1. Isolecithal
2. Mesolecithal
3. Telolecitithal
4. Centrolethical
35
Isolecithal
Little yolk, division throughout
36
Mesolecithal
Medium yolk, more division on top
37
Telolecithal
Large yolk, almost all division on top
38
Centrolethical
Division in random spots
39
First cleavage
Meridonial
40
Second cleavage
Meridonial
41
Third cleavage
Equitorial
42
Fourth cleavage
Unequal cleavage between animal and vegital hemispheres
43
Micromeres
Smallest cells
44
Macromeres
Biggest cells
45
Mesomeres
Medium cells
46
How do the animal and vegetal halves differ
Cells on the bottom have different morphogens than on top
47
7th plus division
At 128 cells, divisions become less regular. Forms blastula
48
How many cells thick is the blastula
One (hollow inside)
49
What do the cells of the blastula adhere to
1. Hyaline layer (outside)
2. Basal membrane (inside)
3. Neighboring cells
50
What develops on the blastula
Cilia
51
What is initiated at the animal pole of the blastula
Hatching (hatches out of fertilization envelope)
52
What changes the osmotic pressure of the blastula
Sodium influx
53
What fills the cavity of the blastula
Proteinaceous fluid fills cavity
54
What expands the blastocoel
Osmotic pressure
55
Mechanisms for establishing asymmetry (in regards to splitting cytoplasmic determinants)
1. Patterning molecules bound to egg cytoplasm
2. Molecules actively transported along the cytoskeleton (made of microtubules in secretory vesciles)
3. Molecules become associated with one centrosome, and then follow that centrosome into one of the two mitotic sister cells
56
What happens when asymmetry is established
One cell can specify another and participate in reciprocal inductions
57
Notochord
Induces spinal cord formation
58
Where is the animal pole located
Top
59
Mesenchyme
Loosely packed, unconnected, mesoderm, neural crest origin
60
Coelom
Internal body wall, mesoderm origin
61
What type of specification do micromeres undergo
Autonomous
62
60 cell stage
Specified but not committed. Blastomeres mostly undergo conditional specification
63
What cells trigger early induction events
Micromeres
64
What do micromeres have enough information to do
Induce recognizable larvae and secondary axis
65
____ plays a role in micromere specification
B-catenin
66
What activates B-catenin
Wnt signal transduction pathway
67
What cell fates does B-cateni accumulate in
Endoderm and mesoderm
68
What do veg2 cells with B-catenin become
Endomesoderm
69
______ causes accumulation of B-catenin in every cell
LiCl, transforms presumative ectoderm into endoderm
70
What will animal cells become if they have B-catenin
Endoderm
71
What micromere protein activates the notch pathway in adjacent veg2 cells
Delta
72
What does notch pathway activation result in
Secondary mesanchyme
73
What is Wnt8 made of
Micromeres and endoderm cells
74
What signal are endomesoderm cells not recieving
Delta
75
What type of signal does Wnt8 act as
Autocrine signal
76
What does Wnt8 boost specification in
Veg2 endoderm and micromeres
77
Invagination
Infolding region of the cells
78
Ingression
Migration of individual cells from the interior surface layer into the interior of the embryo (cells become mesencymal and migrate independently)
79
Involution
In turning or inward movement of an expanding outer layer spreads over the internal surface of the external cell layer
80
Delamination
Splitting one cellular sheet into two parallel sheets
81
Epiboly
Epithelial sheets spread and enclose deeper layers of the embryo
82
Intercalation
Two rows become one
83
How does ingression work
Cells lose cadherin and migrate up the blastocoel to a spot
84
What gradients move cells in ingression
VEGF and FGF (growth factors)
85
What does invagination of the vegetal plate form
Archenteron (primative digestive tract)
86
How does the forgut move to the top
Invagination, involutes inwards
87
What appears to be responsible for the initial invagination that occurs during gastrulation
Osmotic gradient
88
How are cells freed from the hyalin layer to be able to move upward
Changing osmotic gradient
89
What do cells do during formation of the archenteron
Cells intercalate and move forward at the same time (results: thin tube)
90
When is the anterior posterior axis formed
Very early on with the animal vegetal axis
91
What does the vegetal region have that is necessary for posterior development
Maternal components
92
When is the dorsal ventral axis established
After fertilizatio
93
Another name for the dorsal ventral axis
Oral-aboral
94
Where is the dorsal ventral axis
Approx. 45 degrees clockwise from the first cleavage plane
95
What promotes oral fates
Nodal
96
What promotes aboral fates
BMP2/4
97
When is the left right axis established
After oral-aboral
98
The left right axis has ____ expression of the nodal gene
Asymmetric
99
What sets up the axis in amphibians
The organizer
100
What is the organizer analogous to in sea urchins
Mircomeres
101
Inductions of the organizer
- Dorsal ventral axis
- Mesoderm
_Ectoderm
102
Where does fertilization occur
Anywhere on the animal pole
103
Cortical rotation
Contents in egg shift
104
Where are cytoplasmic determinants shifted to
Gray crescent
105
Where is the gray crescent located
Directly diagonal to the site of sperm entry
106
How many degrees does the egg rotate
30
107
What does the first cleavage plane cut in half
Gray crescent
108
Where is the dorsal located
Opposite sperm entry
109
Where does gastrulation begin
Gray crescent
110
What does cortical rotation relocate
Maternal factors
111
What is the dorsal most and vegetal most region
Nieukoop Center `
112
Yolk classification of amphibians
Mesolecithal
113
What pole is the yolk in for amphibians
Vegetal pole
114
Where do more cells develop in the amphibian embryo
Animal pole
115
What type of cleavage occurs in amphibians
Displaced radial
116
Holoblastic
Complete cleavage
117
Meroblastic
Incomplete cleavage
118
Is amphibian cleavage holoblastic or meroblastic
Holoblastic
119
Major functions of blastocoel
1. Permits cell migration during gastrulation
2. Prevents cells beneath it from interacting prematurely with cells above it (cells on top are different from bottom cells)
120
What type of movement forms the archenteron
Invagination
121
Beginning of frog gastrulation
Formation of dorsal lip
Vegetal rotation
Invagination of bottle cells
Involution of marginal zone cells
122
Dorsal blastophere lip
Site where gastrulation begins (cells stream through the opening)
123
What happens to the blastocoel during gastrulation
Will eventually go away and be replaced
124
What does gastrulation form
3 germ layers
125
Where is archenteron located
Blastopore
126
What is the yolk plug
Spot not yet covered
127
What are axes specified by
Events triggered at fertilization and realized during gastrulation
128
What is the mesoderm determined by
Transcription factors and paracrine factors from the vegetal region
129
What is the only tissue in the xenopus pre-gastrula that has its fate determined
Dorsal lip of the blastopore
130
What will the dorsal lip determine the fates of
Notochord and head endomesoderm
131
What decides if it will be ventral or dorsal mesoderm
Nodal
132
Both cells have equal amount of gray crescent
Normal development
133
One cell has entire gray crescent
Normal development of one, only belly piece in other
134
Gray crescent
Future dorsal lip of the blastopore (future site of gastrulation)
135
Transplantation in early gastrula
Conditional specification
136
Transplantation in late gastrula
Autonomous specification
137
Spemann and Mangolds experiment
Dorsal blastopore transplanted to another embryo, secondary axis forms
138
What is the conclusion of the spemann and mangold experiment
The dorsal lip is the organizer
139
What does the organizer do in spemann mangold experiment
- induces the host ventral tube and dorsal mesodermal tissue such as somites
- organized host and donor tissue into secondary embryo with a clear a-p and d-v axis
- organize dorsal ectoderm into neural tube and transform flaking mesoderm into anterior posterior body axis
140
Induction
Signal from one group of cells
141
The mesoderm is induced to be dorsal, intermediate or ventral based on _______
Location
142
Dorsal signal
B-catenin
143
B-Catenin
- anchor for cadherins
| - nuclear transcription factor in wnt
144
B catenin in sea urchins
specifies micromeres and endomesoderm
145
B catenin in xenopus
specifies dorsal structures
146
Where is B catenin initially
Spread throughout the embryo
147
Where does B catenin become accumulated in
Dorsal cells
148
Where is B catenin concentarted
Nieukoop center and organizer
149
Dorsalization of B catenin accomplished by
- Protecting B catenin in the dorsal area
| - Degrading B catenin anywhere else
150
What causes accumulation of B catenin only on dorsal side of the embryo
Cortical rotation
151
What happens to B catenin without Wnt
It is broken down
152
GSK3 distrubution
Distributed throughout the embryo
153
What marks B catenin for degradation
GSK3
154
Dishevled (Dsh)
Blocks GSK3 activity
155
Where is Dsh localized
Cytoplasmic cortex at the vegetal pole
156
GSK3 present
No B catenin, ventral
157
No Gsk3
B catenin present (Dsh blocked GSK3), dorsal
158
Dsh present
B catenin present, dorsal
159
GBP
GSK3 binding protein
160
Kinesin
Motor protein
161
How is Dsh moved
Moved on microtubules. Hitches a ride on GBP. Kinesin helps it move
162
Where is beta catenin present after GSK3 acts
Marginal area opposite the point of sperm entry (ie. future dorsal lip)
163
What transcirption factor does B catenin act with
Tcf3
164
What do B catenin and Tcf3 do
Stimulate expression of dorsalizing genes
165
Dorsalizing genes
Siamois and Twin proteins, Goosecoid and Xlim1
166
Siamois and Twin
Tracription factors to turn on more dorsalizing genes
167
Gooseoid and Xlim1
Specify dorsal mesoderm
168
B catenin pathway (organizer induction)
B catenin --> nodal related high --> organizer (dorsal)
169
VegT, Vg1 pathway (mesoderm or organizer induction)
VegT, Vg1 --> nodal related high --> organizer (dorsal)
OR
VegT, Vg1 --> nodal related low --> ventral mesoderm
170
Summary of mesoderm induction
1. Maternal RNAs tethered to the vegetal cortex
| 2. Gardient of nodal (TGFB family protein) signal
171
Maternal RNAs thethered to vegetal cortex
- Vg (TGFB family protein)
| - VgT (transcription factor)
172
Role of VgT
Instruct endoderm to express another TGFB family activin, derriere and nodal
- Induce to express Xbra or goosecoid
- induce mesodermal development
173
Gradient of nodal signal
Nodal gradient is formed by expression of VgT and B-catenin in endoderm
174
What does nodal gradient induce
Mesoderm formation
175
Less nodal
Ventral mesoderm
176
Intermediate nodal
Lateral mesoderm
177
Highest nodal
The organizer (dorsal)
178
Functions of the organizer
1. Can self differentiate dorsal mesoderm
2. Can dorsalize the surrounding mesoderm into paraxial mesoderm
3. Can initiate the movement of gastrulation
4. Can dorsalize the ectoderm to induce neural tube
179
What does the organizer develop into
1. Pharangyeal ectoderm (frontal ectodermal cells)
2. Head mesoderm (frontal mesodermal cells)
3. Dorsal mesoderm (notochord)
4. Dorsal blstopore lip
180
What does anterior posterior axis development come after
Dorsal ventral axis development
181
What do the first migarting endomesodermal cells become
Anterior part
182
What do later migrating mesoderm cells become
Ventral lips (form posterior structures)
183
Organizer inductions
- Mesoderm
- Dorsal/ventral axis
- Ectoderm and neural tissue
184
What does ectoderm usually want to become
Neural tissue
185
How does ectoderm become epidermis
Needs signa (BMP)
186
BMP inhibitors
Noggin, Chordin, Follistatin
187
What activates BMP inhibitors
Smad 2/4 and Siamois/Twin
188
What do BMP inhibitors do
Stop BMP and make neural tissue
189
Where are BMP inhibitors located
Dorsal side
190
Where is more BMP located
Ventral side
191
What happens as levels of noggin increase
More neural structures develop
192
Nuclear proteins
Remain within the cell
193
Where are noggin, chordin and follistati found
Organizer
194
Epidermal inducers
BMP4, BMP2, BMP7
195
Job of BMPs
Repress genes involved in forming neural tissue while activating other genes involved in epidermal specifiaction
196
Add BMP to embryp
No dorsal structures, no neural tube
197
Blocked BMP in embryo
Spread to ventral side and form more neural tissue than they were supposed to
198
Proneural gene
Neurogenin
199
Making sure parts of the brain are made in the right spot
Regional specification of the neural structures that are produced
200
FrzB
Binds to Wnt and prevents it from binding to receptor on cell and activating it (acts as receptor)
201
What is FrzB secreted from
Organizer (dorsal)
202
Where is Wnt secreted from
Ventral
203
FrzB blocks _____ from dorsal region
Xwnt8
204
When is d-v axis set up
At ferilization
205
When is a-p axis set up
Established by gatsrulation movements across the dorsal lip of the blastopore
206
L-R axis establishment
Nodal expression on left, not righrt
207
Gene that expressed eft right axis
Xnr1
208
How is xnr1 expression limited to the left side
Process involving cortical rotation and Vg1
209
What happens if Xnr1 is blocked
Random gut coiling and heart looping
210
What direction does the heart loop (normal)
Left
211
What direction is gut coiling (normal)
Counter clockwise
212
What happens if nodules are mutated
No left or right axis
213
Yolk amount in mammals
Isolethical
214
How do mammals gastrulate
Gastrulate as if there is a lot of yolk `]
215
What is the blastula called in mammals
Blastocyst
216
When is the first mammalian cleavage
1 day after fertilization
217
How far apart are cleavages in mammals
12-24 hrs
218
Cleavage type mammals
Rotational
219
Rotational cleavage
Not happening with all cells at the same time, no MBT
220
Compaction
8 cell stage, tight junctions between outside cells (e-cadherin), seal off inside of sphere
221
What will ICM form
Embryo proper
222
What will trophoblast form
Extraembryonic structures
223
What secretes hormones to cause the uterus to retain the fetus
Trophoectoderm
224
Cavitation
Trophoblast secretes fluid into the morula (with Na+ pumps, `creates blastocoel and pushes ICM to one side)
225
Zona pellucida
Prevents adhesion to uterine wall
226
Why does adhesion to the uterine wall need to be prevented
Must hatch out for adhesion, premature adhesion = eptopic pregnancy
227
What is formed when trophoblast attaches to the uterine wall
Chorion
228
Chorion
Embryonic portion of the placenta
229
What is secreted by the trophoectoderm and why
Proteases
- Digests uterine ECM
- Blastocyst implants
230
What does ICM form besides embryo proper
Yolk sac, allantois, amnion
231
What does the allantois turn into
Part of the bladder
232
Which is a stem cell, ICM or trophoectoderm
ICM
233
Cells of the blastocyst
ICM and trophoectoderm
234
What does ICM become
Epiblast and Hypoblast
235
Epiblast
Forms embryo proper
236
Hypoblast
forms extraembryonic membrane - yolk sac
237
What are the epiblast and hypoblast together callled
Bilaminar germ disc
238
Cytotrophoblast
- adheres to endometrium
- proteolyze uterine wall
- secretes paracine factors to attract maternal blood vessels
- displaces vascular tissue
239
Syncytiotrophoblast
Digests uterine tissue (move further into uterine wall)
240
Extraembryonic endoderm
Gives rise to the yolk sac
241
Extraembryonic mesoderm
Gives rise to blood vessels and umbilical cord
242
Job of paracrine factors
Recruit maternal blood vessels towards embryo
243
Decidua
Maternal portion of the placenta
244
What does the epiblast become
Amniotic ectoderm or embryonic epiblast
245
Embryonic epiblast division
Embryonic ectoderm of primative streak (which will become embryonic endoderm or embryonic mesoderm, sometimes extraembryonnic mesoderm)
246
What does the hypoblast become
Hypoblast --> extraembryonic endoderm --> yolk sac --> (extraembryonic mesoderm sometimes)
247
What does the trophoblast become (pathway)
Trophoblast --> cytotrophoblast --> syncytiotrophoblast
248
What does the chorion surround
Embryonic membrane
249
What is the cloud around the fetus
Blood vessels, part of the chorion
250
Cells that form yolk sac
hypoblast, blastodisc cells
251
Function of yolk sac
No nutritional function (vestigial), important for blood cell formation
252
What is the amnion formed by
Epiblast... ectodermal and mesodermal cells complete amnion
253
Amniotic fluid purpose
Cushions embryo or fetus
254
Allantois formation
Begins as outpocket of endoderm near yolk sac base, endodermal and mesodermal cells form stalk attaching to blastocyst wall
255
Purpose of allantois before it becomes the bladder
Vestigial respiratory organ
256
What is the chorion formed from
Mesoderm and trophoblast near allantois
257
How does the chorion get nutrients
Chorion vili invade endometrium
258
Placenta purpose
Primary embryo support, oxygen and nutrients exchanged for carbon dioxide and wastes
259
What do umbilical arteries carry
Deoxygenated blood from fetus
260
What do umbilical veins carry
Oxygenated blood to fetus
261
Early twin separation
2 chorions, 2 amnion
262
Middle twin separation
1 chorion, 2 amnion
263
Late twin separation
1 chorion, one amnion
264
Evidence that ICM generate any cell type
Twin formation (ICM split and both halves can become a whole embryo)
265
Where does human gastrulation begin
Primative streak
266
Movement of primative streak
Posterior to anerior, back posterior and disappears
267
What is the primative streak analogous to in amphibians
Blastopore (where movement first starts)
268
Ectoderm
Nonmigrating superficial blastodisc cells
269
Endoderm
Cells facing yolk sac
270
Mesoderm
Poorly organized cells between two other germ layers
271
What day does gastrulation occur in humans
12-15
272
What germ layer is created first in humans
Endoderm
273
Where will the brain form
Neural plate
274
How does the neural tube form
Primative streak loops
275
Where does the neural plate form
In the ectoderm along embryo posterior
276
What forms CNS cavities
Neural folds
277
Week 3
Head fold
Chorionic vili
Heart starts beating
Allantois forms
278
Week 4
Body stalk
Yolk stalk
Other organs form
279
Body stalk
Between the embryo and chorion. Forms carrying blood to and from the placenta
280
Yolk stalk
Narrow connection between endoderm and yolk sac
281
When does embryonic folding occur
4 weeks
282
Week 5
Umbilical stalk
283
What forms the umbilical stalk
Body and yolk stalks
284
Week 6
Brain waves, mouth and lips, fingernails, limbs lengthen, skull bones form
285
When does it become a fetus
9 weeks
286
Week 10
Bones replace cartilage. Fetus is connected to placenta by umbilical cord
Amniotic cavity fills uterine cavity
287
What is the umbilical cord made of
Allantois, blood vessels, remnants of yolk stalk
288
Carnegie stages
Stage based on level of development, regardless of time passed
289
Anterior posterior patterning mammals
BMP, Wnt, RA, Hox genes
290
Dorsal ventral patterning mammals
Mystery
291
Left right patterning mammals
Cilia, Hedgehog, RA, FGF
292
Mammalian organizer
AVE and Node
293
AVE
Anterior visceral endoderm, secretes anterior markers
294
Node
(same as spemann organizer in amphibians), creates all body and neural features
295
Anterior patterning
BMP and Wnt antagonists (some RA)
296
Posterior patterning
Wnt, BMP, FGF, RA
297
Retinoic acid gradient
Posterior --> high, anterior--> low
298
How is the anterior determined
Blocking posterior signals
299
What determines A-P axis patterning
Hox genes
300
What activates hox genes
Cdx1,2,4
301
What activates cdx family
RA, Wnt3a, fgf8
302
Homeotic selector genes
Determine segment identity
303
Where are hox genes expressed
Along the dorsal axis
304
How is the level of body along the A/P axis determined
Most posterior hox gene expressed
305
What does hox knockout do
Shifts vertebrae
306
What are hox genes sensitive to
RA
307
Direction of RA gradient
P-A
308
Where does hypoblast form
Side of ICM exposed to blastocyst fluid
309
Where does dorsal axis form
From ICM cells in contact with trophoblast and amniotic cavity
310
Levels of regulation for left right
Organ specific
| Global
311
Organ specific
IV gene
| Mutations cause randomized LR asymmetry for each organ, can be fatal
312
Global
Inversion of Inv gene
| Mutations cause asymmetrical organs to be reversed, usually not a large problem
313
Active genes on left side
Nodal and Pitx2
314
LR mechanism frog
Vg1 placement
315
LR mechanism chick
Suppression of sonic hedgehog
316
LR mechanism mouse
Asymmetirc distribution of Shh
317
Dynein
Motor protein
318
What cells are ciliated for LR
Node
319
NVP
Nodal vesicular parcels
| Contain Shh and RA
320
What happens if parcels are not secreted
LR asymmetry fails to establish
321
What are cilia powered by
Dynein and ATPase
322
What do iv genes code for
Dynein protein
