Sea Urchins

Question 1

Sea Urchin [iso/meso, mero/homo]

Answer 1

isolecithal, holoblastic cleavage

Question 2

Animal/Vegetable pole

Answer 2

animal = top, vegetal = bottom

Question 3

Cells are equivalent in their content up until the __ cell stage of the embryo

Answer 3

8 cell stage is no longer equivalent

Question 4

At what stage do meso, macro, and micromeres appear?

Answer 4

At the 16 cell stage

Question 5

Oral/Aboral, dorsal/ventral

Answer 5

Oral/ventral, dorsal/aboral

Question 6

Animal Cells produce what tissue type?

Answer 6

Ectoderm

Question 7

Veg 1 forms what tissue type?

Answer 7

Base of archenteron and ectoderm

Question 8

Veg 2 forms what tissue type?

Answer 8

endoderm and secondary mesenchyme

Question 9

Micromeres form what tissue type?

Answer 9

skeletogenic mesenchyme (spicules)

Question 10

Hyaline layer

Answer 10

Clear layer surrounding the embryo, but not part of the fertilization envelope

Question 11

Blastopore

Answer 11

Slight ingression at the vegetal pole

Question 12

Pluteus

Answer 12

Sea urchin that looks like an easel

Question 13

What conclusion was made concerning the vegetal half of the embryo?

Answer 13

It has the determinants to create mesoderm and endoderm

Question 14

What happens when you remove the pigment band?

Answer 14

You lose mesoderm and endoderm.

Question 15

When transplanting micromeres, what happens?

Answer 15

The micromeres induce endoderm formation and primary mesenchyme bundles.

Question 16

What molecule seems to be creating induction from micromeres?

Answer 16

Nuclear Beta Catenin

Question 17

Where is nuclear beta catenin found?

Answer 17

Highest levels in the micromeres , followed by the veg 2 cells.

Question 18

How is beta catenin regulated?

Answer 18

Quality of disheveled that inhibits its destruction

Question 19

Where is disheveled usually found?

Answer 19

at the vegetal pole of the egg, and the micromere cortex

Question 20

Wnt 6

Answer 20

important for endoderm formation by expression of FoxA

Question 21

Frizzled 7

Answer 21

Important receptor for Beta catenin production in macromeres.

Question 22

Nodal is part of what family of proteins?

Answer 22

TGF Beta Proteins that involve phosphorylation of Smads and transcription factors.

Question 23

Nodal is important in determining which orientation?

Answer 23

The left right asymmetry, with more nodal in the oral side first, then the right side. Without nodal, the embryo does not show a bilateral symmetry.

Question 24

EMT transition occurs with the ___ ___ cells. Cells lose adhesion to ___ and ___, but use adhesion with ___ to pull themselves into the interior.

Answer 24

Primary mesenchymal cells undergo EMT, losing connection with hyaline layer and other cells, but grabbing onto the basal lamina.

Question 25

Vegetal Plate

Answer 25

Thicker layer of cells at bottom of blastula used to protrude the archenteron.

Question 26

What morphogenic movement is needed to continue expansion of the archenteron?

Answer 26

Convergent Extension

Question 27

What shape of cells are needed for primary invagination?

Answer 27

Bottle cells

Question 28

What evidence is there of convergent extension in the archenteron?

Answer 28

The circumference becomes thinner, and when staining cells, it is clear that they go every other.

Question 29

What are the names of the extensions protruding from the secondary mesenchyme at the tip of the archenteron?

Answer 29

Filopodia

Question 30

At what stage is filopodia necessary?

Answer 30

After about a third of the archenteron. This means that the embryo is initially capable of convergent extension on its own, but needs additional help from the secondary mesenchyme filopodia.

Question 31

Attachment to the hyaline layer is needed for ___

Answer 31

invagination

Question 32

Attachment to the basal lamina is needed for ___

Answer 32

Proper orientation and movement of the archenteron

Question 33

Two skeletogenic clusters form on the ___ side of the embryo

Answer 33

Ventral (oral) side

Question 34

What experiments were done with NiCl2, and what does it tell us about spicule formation?

Answer 34

Experiments were done with all combinations of either hard metal blastulas, or hard metal PMCs. PMC’s are influence to create their patterns by their environments. The healthy PMC in a NiCl blastula was incorrect, but an NiCl PMC in a healthy blastula was fine.

Question 35

What growth factor in involved in spicule pattern formation?

Answer 35

FGF (fibroblast growth factor)

Question 36

What happens if you cause a dimple on the side of blastula in order to get the archenteron to attach

Answer 36

Nothing, but if you make the dimple at the top, the archenteron ceases growing as soon as it touches the top.