Frogs

Question 1

Which side of the embryo does the organizer form?

Answer 1

The dorsal side of the embryo.

Question 2

What can the organizer induce cells into?

Answer 2

Neural ectoderm

Question 3

What are three spots on the early frog blastula that can be distinguished by their color?

Answer 3

The Pigmented animal region, gray crescent, and vegetal region.

Question 4

Why is the gray crescent visible?

Answer 4

The subcortical crescent is visible after the outer surface of the zygote rotates.

Question 5

What happens without inclusion of the gray crescent?

Answer 5

You do not have formation of axial structures, and you get a “belly-piece”: Bauschstuck, or Chicken McNugget

Question 6

What is the orientation of the cortical rotation, and crescent with respect to the sperm entry point?

Answer 6

The sperm entry point is defined as the ventral side. The cortex rotates 30 degrees, the gray crescent is on the dorsal side.

Question 7

What evidence is there that cortical rotation is a required movement?

Answer 7

A UV irradiated zygote cannot undergo rotation, and ends up as a chicken mcnugget. If tipped in wax, the embryo is rescued.

Question 8

What cellular component is necessary for cortical rotation?

Answer 8

Microtubules

Question 9

What happens with an excess of microtubules?

Answer 9

excess of anterior structures.

Question 10

Are frog eggs in zero gravity normal, or abnormal?

Answer 10

Normal. Microtubules and motors are sufficient for rotation.

Question 11

What induces functional organizer?

Answer 11

Dorsal vegetal cells from the Nieuwkoop Center.

Question 12

Dorsal endoderm induces dorsal endoderm. What evidence is there for this?

Answer 12

If you remove the Mesoderm from a blastula, the ectoderm that is now touching the endoderm turns to mesoderm.

Question 13

What are some molecular accumulations in the dorsal endoderm?

Answer 13

Release of Disheveled, GSK-3 (inhibits GSK-3B which would normally break down B catenin), and Wnt 11

Question 14

What can cause a Nieuwkoop Center to form?

Answer 14

B catenin

Question 15

What happens when you deplete B catenin?

Answer 15

YOU have centralized embryos.

Question 16

What does B-catenin cause expression of by the Nieuwkoop Center?

Answer 16

Siamois, and twin genes.

Question 17

What does siamos over expression lead to ?

Answer 17

A second axis.

Question 18

Mesoderm Induction : Step 1

Answer 18

Beta catenin leads to expression of nodal related proteins like VegT and Vg1

Question 19

Mesoderm Induction: Step 2

Answer 19

Vegetal cells create a spectrum of D-V differences

Question 20

Mesoderm Induction: Step 3

Answer 20

Mesoderm is induced by vegetal cells that contain those nodal proteins in a spectrum.

Question 21

How does the Organizer work? Broad

Answer 21

The Organizer inhibits centralizing growth factors

Question 22

What are some ventral growth factors?

Answer 22

BMPs and Wnt 8

Question 23

What are some Organizer factors?

Answer 23

Chordin, Noggin, FrzB,Dikkopf, and Cerberus

Question 24

What Organizer factors inhibit BMPs?

Answer 24

Noggin and Chordin

Question 25

What Organizer factors inhibit Wnt 8?

Answer 25

FrzB, Dickkopf, and Cerberus.

Question 26

What type of tissue does BMP usually lead to?

Answer 26

epidermis

Question 27

Without ventral signals, ectoderm influenced by the Organizer becomes

Answer 27

neural ectoderm

Question 28

After gastrulation in the frog, Organizer mesoderm lies where in relation to ectoderm?

Answer 28

In a layer beneath the ectoderm.

Question 29

Difference between superficial and deep cells

Answer 29

Superficial cells are on the surface as epithelial cells, and are joined by junctions. Deep cells are more loosely organized, and can move around more independently.

Question 30

Dorsal blastopore lip formation

Answer 30

Induced by invagination from bottle cells

Question 31

What do the deep cells, superficial cells, and dorsal mesoderm of the marginal zone form respectively?

Answer 31

Deep cells form mesoderm, superficial cells form endoderm, and the dorsal marginal zone mesoderm form the Organizer.

Question 32

NIMZ

Answer 32

Non-involuting marginal zone

Question 33

What do the dorsal and ventral NIMZ form?

Answer 33

Dorsal non involuting marginal zone become neural ectoderm, and the ventral non-involuting marginal zone become epidermis.

Question 34

IMZ

Answer 34

Involuting marginal zone

Question 35

What do the deep cells and superficial cells of the IMZ become?

Answer 35

Deep cells of IMZ become organizer mesoderm, and superficial dorsal IMZ becomes roof of the archenteron

Question 36

What happens to bottle cells during gastrulation?

Answer 36

They constrict to start the dorsal blastopore lip, and spread to the roof of the archenteron.

Question 37

LEM

Answer 37

leading edge mesoderm, involutes first, becomes head, heart, and liver

Question 38

What morphogenic movement do the animal cap cells perform?

Answer 38

Epiboly via radial intercalation

Question 39

What morphogenic movement do the bottle cells perform?

Answer 39

Invagination by apical constriction, then respreading

Question 40

What morphogenic movement does the non-involuting marginal zone perform (NIMZ)?

Answer 40

Radial intercalation, followed by convergent extension

Question 41

What morphogenic movement does the involuting marginal zone perform (IMZ)?

Answer 41

Convergent extension

Question 42

What experiment shows convergent extension of the IMZ and NIMZ?

Answer 42

Keller's excising of NIMZ and IMZ produces extension into neural ectoderm and mesoderm.

Question 43

What mechanics underly convergent extension?

Answer 43

Cell become polarized extending protrusions along the axis of extension via myosin II and the planar cell polarity pathway.

Question 44

What kind of signaling is necessary for convergent extension?

Answer 44

Planar Cell Polarity Pathway

Question 45

What kind of motor protein is required for convergent extension?

Answer 45

Myosin II

Question 46

How does leading edge mesoderm move, and what orients the process?

Answer 46

The leading edge mesoderm extends lamelopodia that crawl along oriented fibronectin fibrils that are attached to the inner face of the blastocoel

Question 47

What is special about the axolotl ambystoma mexicanum?

Answer 47

Useful for studying leading edge mesoderm, and it exhibits neoteny, (becomes reproductively mature while maintaining juvenile (larval) characteristics.

Question 48

What are fibronectin fibrils usually oriented as?

Answer 48

From anterior to posterior

Question 49

How do you distrupt fibronectin fibrils, and what happens?

Answer 49

You add antibodies that are not polarized, and mesoderm can no longer migrate or involute. You get a brain looking animal pole.