gastrulation in xenopus and zebrafish II

Question 1

What does BMP bind to?

Answer 1

serine threonine kinase receptor

Question 2

What happens when BMP binds to its receptor?

Answer 2

The type II receptor is activated and phosphorylated, leading to the phosphorylation of the type I receptor

Question 3

What does the type I BMP receptor do once phosphorylated?

Answer 3

Phosphorylates a series of Smad proteins (1, 5, 8)

Question 4

Result of Smad proteins 1, 5, 8 being phosphorylated?

Answer 4

Recruit Smad 4 which moves to the nucleus and activate target genes

Question 5

Difference between BMP and nodal, TGFbeta and Activin?

Answer 5

BMP activates Smad 1,5,8, the others activate Smad 2,3

Question 6

Result of activating Smad 2,3?

Answer 6

Activation of Smad4 which enters the nucleus and activates target genes

Question 7

What is BMP signalling important in?

Answer 7

Centralisation of the mesoderm

Question 8

What are Nodal, TGFbeta and Activin important in?

Answer 8

Specifying dorsal fates

Question 9

What are maternal factors?

Answer 9

mRNAs that are depositied within the egg during oogenesis that play a role in establishing the axis of the embryo

Question 10

WHich pole is typically pigmented?

Answer 10

Animal pole

Question 11

Which pole is the nucleus in?

Answer 11

ANimal

Question 12

Which mRNA is in the animal pole?

Answer 12

Tcf1

Question 13

Which mRNA is in the vegetal pole?

Answer 13

VegT, Dsh, Xwnt11

Question 14

WHich germ layer does the animal pole contribute to?

Answer 14

Ectoderm

Question 15

WHich germ layer does the vegetal pole contribute to?

Answer 15

Endoderm

Question 16

When does the mesoderm become specified?

Answer 16

During gastrulation

Question 17

Where are the signals that induct mesoderm from?

Answer 17

Blastula

Question 18

How are the vegetal and animal region involved in mesoderm formation?

Answer 18

Vegetal signals act on cells in animal region to specify a band of prospective mesoderm around the equator of the blastula

Question 19

What are dorsalizing factors?

Answer 19

VegT, Dsh and Xwnt

Question 20

What does the sperm fusion cause?

Answer 20

cortical rotation–> dorsalizing factors move to side by ab 30 degrees

Question 21

Effect on dorsal factors of the sperm fusion?

Answer 21

The future dorsal side of the amphibian embryo develops opposite to the site of sperm entry

Question 22

Where does the blastopore appear?

Answer 22

Opposite to where the sperm fused–> where the dorsalizing factors are

Question 23

When is the dorsal ventral axis extablished?

Answer 23

4-cell stage, b4 gastrulation

Question 24

What do the cells on the side of the embryo that has the dorsalising factors have?

Answer 24

Active Wnt, so beta catenin doing its thing

Question 25

What does beta catenin lead to the expression of?

Answer 25

Siamois TF

Question 26

What does siamois expression lead to?

Answer 26

Formation of the Nieuwkoop centre

Question 27

What is the Nieuwkoop centre?

Answer 27

First important signalling centre that helps direct gastrulation and the expression of the germ layers

Question 28

What happens if there are two Nieuwkoop centres?

Answer 28

An embryo w/ a twinned axis develops

Question 29

What does the Nieuwkoop centre instruct?

Answer 29

A region above it to become the Spemann organizer

Question 30

What do the combined effect of activating beta catenin and Vegt do?

Answer 30

activates siamois, which in turn activates nodal