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Embryonic Development > Frogs > Flashcards

Frogs Flashcards

1
Q

Which side of the embryo does the organizer form?

A

The dorsal side of the embryo.

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2
Q

What can the organizer induce cells into?

A

Neural ectoderm

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3
Q

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

A

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

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4
Q

Why is the gray crescent visible?

A

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

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5
Q

What happens without inclusion of the gray crescent?

A

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

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

What cellular component is necessary for cortical rotation?

A

Microtubules

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9
Q

What happens with an excess of microtubules?

A

excess of anterior structures.

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10
Q

Are frog eggs in zero gravity normal, or abnormal?

A

Normal. Microtubules and motors are sufficient for rotation.

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11
Q

What induces functional organizer?

A

Dorsal vegetal cells from the Nieuwkoop Center.

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12
Q

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

A

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

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13
Q

What are some molecular accumulations in the dorsal endoderm?

A

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

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14
Q

What can cause a Nieuwkoop Center to form?

A

B catenin

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15
Q

What happens when you deplete B catenin?

A

YOU have centralized embryos.

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16
Q

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

A

Siamois, and twin genes.

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17
Q

What does siamos over expression lead to ?

A

A second axis.

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18
Q

Mesoderm Induction : Step 1

A

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

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19
Q

Mesoderm Induction: Step 2

A

Vegetal cells create a spectrum of D-V differences

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20
Q

Mesoderm Induction: Step 3

A

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

21
Q

How does the Organizer work? Broad

A

The Organizer inhibits centralizing growth factors

22
Q

What are some ventral growth factors?

A

BMPs and Wnt 8

23
Q

What are some Organizer factors?

A

Chordin, Noggin, FrzB,Dikkopf, and Cerberus

24
Q

What Organizer factors inhibit BMPs?

A

Noggin and Chordin

25
Q

What Organizer factors inhibit Wnt 8?

A

FrzB, Dickkopf, and Cerberus.

26
Q

What type of tissue does BMP usually lead to?

A

epidermis

27
Q

Without ventral signals, ectoderm influenced by the Organizer becomes

A

neural ectoderm

28
Q

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

A

In a layer beneath the ectoderm.

29
Q

Difference between superficial and deep cells

A

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.

30
Q

Dorsal blastopore lip formation

A

Induced by invagination from bottle cells

31
Q

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

A

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

32
Q

NIMZ

A

Non-involuting marginal zone

33
Q

What do the dorsal and ventral NIMZ form?

A

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

34
Q

IMZ

A

Involuting marginal zone

35
Q

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

A

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

36
Q

What happens to bottle cells during gastrulation?

A

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

37
Q

LEM

A

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

38
Q

What morphogenic movement do the animal cap cells perform?

A

Epiboly via radial intercalation

39
Q

What morphogenic movement do the bottle cells perform?

A

Invagination by apical constriction, then respreading

40
Q

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

A

Radial intercalation, followed by convergent extension

41
Q

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

A

Convergent extension

42
Q

What experiment shows convergent extension of the IMZ and NIMZ?

A

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

43
Q

What mechanics underly convergent extension?

A

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

44
Q

What kind of signaling is necessary for convergent extension?

A

Planar Cell Polarity Pathway

45
Q

What kind of motor protein is required for convergent extension?

A

Myosin II

46
Q

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

A

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

47
Q

What is special about the axolotl ambystoma mexicanum?

A

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

48
Q

What are fibronectin fibrils usually oriented as?

A

From anterior to posterior

49
Q

How do you distrupt fibronectin fibrils, and what happens?

A

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

Embryonic Development (30 decks)

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