Axis Specification in Other Vertebrates

Question 1

Blastodisc

Answer 1

The cell on the top at the very beginning of cleavage. Above the Yolk cell

Question 2

How many nuclei exist in the yolk cell

Answer 2

multinucleate yolk cell

Question 3

What is the name of the single cell layer on the surface of the zebrafish?

Answer 3

The EVL enveloping layer

Question 4

Mid layer of cells in zebrafish

Answer 4

Yolk syncytial layer

Question 5

What does the YSL contain?

Answer 5

multi nuclei with mRNA and proteins important for axial patterning. It also helps pull the enveloping layer down toward the vegetal pole.

Question 6

Difference between hypoblast and epiblast

Answer 6

The hypoblast forms a floor for the embryo connecting the cellular portion to the yolk. Epiblast is surface layer that will eventually involute.

Question 7

What is the equivalent of the Organizer in zebrafish, and where does it form?

Answer 7

The shield forms on the dorsal midline.

Question 8

What other factors are similar to frogs in zebrafish?

Answer 8

B catenin, Bozozok transcription factor similar to Nieuwkoop Center, Nodal,

Question 9

What evidence is there the the shield is like the Organizer?

Answer 9

The shield inhibits ventral signaling, example being loss of Smad5 dorsalizes an embryo

Question 10

Morphogenic Movements: Enveloping Layer and deep cells of epiblast

Answer 10

Deep cells undergo radial intercalation to thin the epiblast and extend like epiboly

Question 11

What happens when the E Cadherin half-baked is removed?

Answer 11

Radial intercalation is no longer possible. Leads to incomplete gastrulation.

Question 12

How is it postulated that the hypoblast forms?

Answer 12

Delamination

Question 13

Epiblast cells involute, but ___ cells don’t

Answer 13

forerunner cells

Question 14

Morphogenic Movements: Axial mesoderm

Answer 14

convergent extension

Question 15

Why is PCP important?

Answer 15

It allows cells to extend filopodia in the proper direction to crawl along fibronectin.

Question 16

List some transcription factors from anterior to posterior

Answer 16

Otx2 - transcription factor expressed in anterior for future brain.
RA - anterior and posterior, but not mid
FGF/Wnt - posterior

Question 17

What are the three layers in the chick beginning cellular thing?

Answer 17

Area pellucida on the inside, marginal zone between pellucida and area opaca.

Question 18

The posterior forms ___ to the long axis of the eggshell

Answer 18

orthogonal

Question 19

The hypoblast forms from two sources:

Answer 19

The epiblast cells engressing, and others migrating forward from the posterior marginal zone.

Question 20

What is the equivalent of the Nieuwkoop in chick cells?

Answer 20

Koller’s sickle.

Question 21

Where does the embryonic endoderm form from?

Answer 21

Mesoderm ingresses through primitive streak.

Question 22

What is the equivalent of the blastopore in the chick?

Answer 22

the primitive streak

Question 23

What is the equivalent of the blastopore lip in the chick?

Answer 23

Henson’s node

Question 24

In the chick embryo, where does definitive endoderm come from?

Answer 24

The epiblast

Question 25

In the chick embryo, where does the notochord tissue come from?

Answer 25

From notochord mesoderm that moves anteriorly after entering Henson’s node.

Question 26

What formation leads to the formation of Henson’s node?

Answer 26

Koller’s Sickle

Question 27

How does Henson’s Node create the rest of the notochord?

Answer 27

It regresses and leaves a notochord in it’s wake.

Question 28

What evidence is there that Henson’s Node acts like the Organizer?

Answer 28

Transplantation of Henson’s Node to another embryo induces a second axis and neural tube.

Question 29

What two molecule presences or absences indicate that Henson’s Node is like Organizer?

Answer 29

Henson’s node produces Chordin, and where Henson’s node does not exist, there is BMP.