Developmental Biology Final

Front 1

What are the 3 axes of a biologically symmetrical animal?

Back 1

Midsaggital plane
Transverse plane
Horizontal plane

Front 2

What type of symmetry does the frog egg have along it's animal vegetal pole?

Back 2

Radial Symmetry

Front 3

Which hemisphere is more heavily pigmented in the newly fertilized frog egg?

Back 3

Pigmented Animal Region

Front 4

Which hemisphere of the newly fertilized frog egg is unpigmented?

Back 4

Vegetal pole

Front 5

Where can fertilization occur in the amphibian embryo?

Back 5

Anywhere in the animal hemisphere

Front 6

What does the site of sperm entry become in frog eggs?

Back 6

The site of sperm entry becomes the Ventral side of the embryo

Front 7

What are the microtubules organized by the centrioles used to accomplish?

Back 7

Separates the cortical cytoplasm from the yolky internal cytoplasm. These tracks allow the cortical cytoplasm to rotate with respect to the inner cytoplasm. They appear right before rotation and disappear right after rotation.

Front 8

What does the 30 degree rotation of the cortical cytoplasm make way for?

Back 8

The grey crescent, which is where gastrulation occurs

Front 9

Where does gastrulation begin in relation to the point of sperm entry?

Back 9

The site opposite from sperm entry

Front 10

What type of cleavage do Amphibians undergo?

Back 10

Holoblastic Cleavage Mesolecithal, displaced radial cleavage

Front 11

When do most of the cells form during early development of the frog, Cleavage or Gastrulation?

Back 11

Cleavage

Front 12

When does the second cleavage furrow begin ofr radial holoblastic cleavage?

Back 12

The first cleavage is still cleaving the yolky portion of the vegetal hemisphere, when the second cleavage begins at the animal pole.

Front 13

Which region cleaves faster the vegetal pole or the animal pole?

Back 13

The animal pole. Cleavage occurs much slowerin the vegetal pole because it contains much more yolk.

Front 14

What is the pattern of the first three cleavages in the frog embryo?

Back 14

1. Meridianal
2. Meridianal
3. Equatorial

Front 15

T/F
The third cleavage occurs at the equator.

Back 15

False
The third cleavage is equatorial but it is displaced towards the animal pole due to yolk distribution. The result is 4 small animal micromeres and 4 large vegetal macromeres

Front 16

At which point do the blastomeres cease to divide at the same rate?

Back 16

After the 12th cleavage

Front 17

After 12th cleavage occurs, which region's blastomeres proliferate more quickly?

Back 17

The animal region

Front 18

T/F
The cell cycles of early Xenopus blastomeres are regulated by MPF in the cytoplasm. There are no gap stages in the xenopus cell cycle for the first 12 divisions and there is no growth between divisions.

Back 18

True

Front 19

An amphibian embryo containing 16-64 cells is called a ______.

Back 19

Morula
(latin means mulberry)

Front 20

When is the frog embryo considered a blastula?

Back 20

When the blastocoel becomes apparent at the 128-cell stage

Front 21

What are the two major functions the blastocoel provides?

Back 21

1. It prevents cell migration during gastrulation
2. It prevents the cells beneath it from interacting prematurely with the cells above it.

Front 22

What events occur during early gastrulation?

Back 22

The bottle cells of the margin move inqard to form the dorsal lip of the blastopore, and the mesodermal precursors involute under the roof of the blastocoel. AP marks the position of the animal pole, which will change as gastrulation continues.

Front 23

What occurs during midgastrulation in the frog embryo?

Back 23

The archenteron forms and displaces the blastocoel, and cells migrate from the lateral and ventral lips of the blastopore into the embryo. The cells of the animal hemisphere migrate down into the vegetal region, moving the blastopore to the region near the vegetal pole.

Front 24

What happens in frog late gastrulation?

Back 24

The blastocoel is obliterated. The embryo becomes surrounded by ectoderm. The endoderm has been internalized and the mesodermal cells become positioned between the ectoderm and endoderm.

Front 25

What is the IMZ?

Back 25

The Involuting Marginal Zone where vegetal rotation pushes the prospective pharyngeal endoderm to the side of the blastocoel

Front 26

What is the infolding of cell sheet into embryo?

Back 26

Invagination
Sea urchin endoderm

Front 27

What is an inturning of cell sheet over the basal surface of an outer layer?

Back 27

Involution
Amphibian mesoderm

Front 28

What is migration of individual cells into the embryo?

Back 28

Ingression
Sea urchin mesoderm

Front 29

What is splitting or migration of one sheet into two sheets?

Back 29

Delamination
Mammalian and bird hypoblast formation

Front 30

What is the expansion of one cell sheet over other cells?

Back 30

Epiboly
ectoderm formation in amphibians, sea urchins, and tunicates

Front 31

What occurs during the intercalation stage of gastrulation?

Back 31

Several layers of the involuting marginal zone intercalate radially to form a broad thin layer. The intercalation extends the IMZ vegetally

Front 32

What happened in Spemann's first newt experiment?

Back 32

He constricted the cell membrane with a hair at the 8 cell stage and all the nuclei were located on one side.
At the 16 cell stage a nucleus escaped over to the other side and as a result two identical salamanders form.

Front 33

What happens if you perform Spemann's intitial experiment with the constriction still longitudinal but perpendicular to the first plane of cleavage?

Back 33

One side will still produce a normal embryo, but the other side became an unorganized tissue mass of ventral cells, which spemann called the bauchstuck or belly piece

Front 34

What is the function of bottle cells in amphibian gastrulation?

Back 34

Bottle cells appear to function by creating a local invagination. At the same time, their cell bodies push inward, forcing deep material upward. The combined effect appears to be to roll the material of the marginal zone to create an incipient blastopore lip. The result is that the leading edge mesoderm

Front 35

What do dorsal marginal zone cells give rise to?

Back 35

dorsal lip of the blastopore

Front 36

What happened when dorsal marginalizing cells were placed on the inner prospective endoderm tissue?

Back 36

They formed bottle cells and sank below the surface of the inner endoderm. As they sank, they created a groove like the early blastopore

Front 37

What is happening in this picture?

Back 37

Vegetal cells underlying the prospective dorsal blastopore lip region are responsible for causing the initiation of gastrulation. This shows that transplanting cells from the vegetal region in a 64-cell embryo can save an irradiated embryo.

Front 38

What is happening in this picture?

Back 38

transferring the most dorsal vegetal blastomeres into the ventral most vegetal region of a normal embryo creates a new gastrulation site.

Front 39

What tissues do the animal cap cells, marginal cells, and vegetal cells become respectively?

Back 39

Ectoderm
Mesoderm
Endoderm

Front 40

What happens when animal cells are combined with vegetal cap cells?

Back 40

Many of the animal cells generate mesodermal tissue

Front 41

What causes mesoderm to form?

Back 41

Signals from the vegetal cells

Front 42

What happens when prospective neural tissue from an early gastrulae was transplanted to the region fated to become belly skin?

Back 42

The neural tissue became epidermal. This means that they were not commited to a specific fate.

Front 43

What happens when prospective neural tissue from an late gastrulae was transplanted to the region fated to become belly skin?

Back 43

Neural plate tissue formed in the region. The tissue's fate had already been determined.

Front 44

What type of development occurs in the early gastrula?

Back 44

Regulative (conditional or dependent) development, because their ultimate fates depend on their location in the embryo.

Front 45

What type of development occurs in the late gastrula?

Back 45

autonomous (independent or mosaic) development. Their prospective fate was said to be determined.

Front 46

What is the result of grafting donor dorsal blastopore into host gastrula?

Back 46

Another gastrulation site occurs and a mirror imaged clone appears, attached at the belly

Front 47

So what model did Niewkoop and Nakamura develop showing mesodermal induction by vegetal endoderm?

Back 47

Mesoderm inducing signals are produced by vegetal cells. The Nieuwkoop center produces dorsal mesoderm inducing signals to the organizer.

Front 48

What is going on prior to fertilization?

Back 48

Dishevelled & GBP associates with kinesin at the vegetal pole of the unfertilized egg

Front 49

What is going on after fertilization?

Back 49

Cortical Rotation
After fertilization, Dsh protein vesicles are translocated dorsally along subcortical microtubule tracks

Front 50

What is occuring in the blown up section?

Back 50

Fast transport on microtubules & Slow transport from cortical rotation
Dsh & GBP bind to and block the action of GSK3, thereby preventing the degradation of beta-catenin on the dorsal side of the embryo.

Front 51

What is occuring in (C)?

Back 51

Dorsal enrichment of Dsh and GBP.
Dsh and GBP are released from kinesin and distributed in the dorsal 1/3 of the embryo

Front 52

What is happening in (D)?

Back 52

Dorsal inhibition of GSK3
Dsh and GBP bind to & block the action of GSK3, preventing degradation of beta-catenin on the dorsal side of the embryo.

Front 53

What is occuring in (E)?

Back 53

Dorsal enrichment of beta-catenin.
The nuclei of the blastomeres in the dorsal region of the embryo receive beta-catenin, while the nuclei of those in the ventral region do not.

Front 54

What is the net result of Dsh on beta-catenin?

Back 54

Dsh stabilizes beta-catenin in the dorsal portion of the amphibian egg

Front 55

What is the Wnt Signal Transduction Pathway?

Back 55

Wnt binds to Frizzled, activating Disheveled, which inhibits GSK-3, which releases beta-catenin to enter into the nucleus for transcription.

Front 56

How does beta-catenin induce the organizer in dorsal mesoderm?

Back 56

1. Microtubules translate Dsh to the dorsal side of the embryo.
2. Dsh binds GSK3, allowing beta-catenin accumulation in the dorsal of the embryo.
3. During Cleavage, beta-catenin enters the nuclei and binds siamois and twin.
4. siamois and twin interact with tf activated by the TGF-beta pathway to activate the gooscoid gene in the organizer
5. Gooscoid is a tf that activates genes responsible for making proteins for the organizer.

Front 57

At late blastula stages, what proteins are localized in the dorsal region and what are localized in the vegetal hemisphere respectively?

Back 57

Beta catenin in dorsal hemisphere
Vg1 & VegT in Vegetal hemisphere

Front 58

What happens during stage 9 of gastrulation?

Back 58

beta-catenin acts with vegT & Vg1 to activate the Nodal-related Xnr genes, creating a gradient of Xnr across the endoderm, highest in the dorsal region.

Front 59

What specifies the mesoderm during gastrulation?

Back 59

The Xnr gradient.
1. Regions with little Xnr have high levels of BMP4 & Xwnt8 and become Ventral mesoderm.
2. Intermediate regions of Xnr become lateral mesoderm.

3. High concentrations of Xnr, goosecoid, and other dorsal tissue becomes the organizer.

Front 60

What are the functions of the Organizer?

Back 60

1. Self-differentiate dorsal mesoderm
2. Dorsalize the surrounding mesoderm into paraxial (somite forming) mesoderm
3. Dorsalize the ectoderm, inducing formation of the neural tube
4. Initiate movements of gastrulation

Front 61

What organizer molecules inhibit BMPs?

Back 61

Chordin Noggin Follistatin all inhibit BMP4, protecting the organizer from being ventralized.
bind to bmp being released, which would ventralize the embryo.

Front 62

What upregulated BMP inhibitors?

Back 62

goosecoid is a tf that leads to BMP inhibitors like chordin noggin and follistatin

Front 63

Why would noggin rescue an irradiated embryo?

Back 63

BMP inhibitor, prevents the mesoderm from being ventralized

Front 64

What are the Wnt inhibitors?

Back 64

Cerberus, Frzb, Dickkopf

Front 65

What is the mechanism for how the mesoderm induces the ectoderm to form the neural tissue?

Back 65

Ectoderm is induced to form epidermis. Ectoderm's default pathway forms neural tissue.

Front 66

Why wouldn't animal ectoderm form epidermis?

Back 66

The ability of the bmps and the Wnts from forming the tissue above them

Front 67

Why wouldn't animal ectoderm form epidermis?

Back 67

The ability of the bmps and the Wnts from forming the tissue above them

Front 68

What is the result of transplanting the dorsal lip of a young gastrula?

Back 68

Young dorsal lips induce anterior dorsal structures when transferred into early newt gastrulae

Front 69

What is the result when older dorsal lips is transplanted into early newt gastrulae?

Back 69

Older produce more posterior dorsal structures

Front 70

If the archenteron roof portion is transplanted into early gastrula then ________

Back 70

we get a head with balancers

Front 71

What are the inhibitors of Wnt?

Back 71

Cerberus, Dickkopf, Frzb, IGF

Front 72

What are inhibitors of BMPs?

Back 72

IGF, Chordin, Noggin, Follistatin

Front 73

Which factors inhibit both Wnts & BMPs?

Back 73

Cerberus & IGF

Front 74

What combination of BMP and Wnt forms Epidermis?

Back 74

BMP activce
Wnt active

Front 75

What combination of BMP and Wnt forms Trunk and spinal cord?

Back 75

BMP Inhibited
Wnt Active

Front 76

What combination of BMP and Wnt forms Head and Brain?

Back 76

BMP Inhibited
Wnt Inhibited

Front 77

What gradient specifies the frog dorsal ventral axis?

Back 77

BMP expression

Front 78

What gradient specifies the anterior posterior axis?

Back 78

Wnt gradient

Front 79

When does ovulation occur in mammals?

Back 79

Metaphase of the 2nd Meiotic division

Front 80

What type of cleavage do mammals undergo?

Back 80

Mammals undergo rotational cleavage. They are isolecithal eggs (small amount of yolk, evenly distributed), holoblastic cleavage

Front 81

What allows MPF to be made and cleavage to occur rapidly?

Back 81

Stored cyclin B

Front 82

What transcription factors are expressed at the 8 cell stage?

Back 82

Cdx2, Oct4, ...

Front 83

Which tf is down regulated after the 4th cleavage?

Back 83

Oct4

Front 84

Which tf is upregulated after 4th cleavage?

Back 84

Stat 3

Front 85

What does nanog do to epiblast cells?

Back 85

Cause them to become hypoblasts

Front 86

What does the basal lamina secrete?

Back 86

collagen, fibronectins and proteoglycans