Deck 4: Laying Down the Vertebrate Body Plan: Xenopus and Zebrafish

Question 1

The amphibian egg is radially symmetric along the animal-vegetal axis. What "breaks" this symmetry?

A) Localization of maternal RNAs to the vegetal pole
B) Fertilization
C) Localization of maternal RNAs to the animal pole
D) Cleavage

Answer 1

B

Question 2

Removing the ventral blastomeres from a four-cell amphibian embryo gives rise to an embryo lacking which tissue?

A) Notochord
B) Neural tube
C) Somites
D) Gut

Answer 2

D

Question 3

What is the dorsal vegetal region that induces the Spemann-Mangold organizer in an amphibian embryo?

A) Animal cap
B) Nieuwkoop center
C) Marginal zone
D) Vegetal center

Answer 3

B

Question 4

Which of the options given would not be an expected way of forcing premature onset of the mid-blastula transition?

A) Injecting extra DNA into the egg
B) Injecting extra cytoplasm into the egg
C) Forcing two sperm to enter the egg
D) Removing some cytoplasm from the egg

Question 5

Which of the following does not send signals that directly induce and pattern the mesoderm?

A) Vegetal blastomeres
B) Animal blastomeres
C) Dorsal mesoderm
D) Ventral mesoderm

Question 6

Which of the following is not true of the role of BMPs in mesoderm patterning?

A) Overexpression of BMPs ventralizes the embryo
B) Introduction of a dominant-negative BMP receptor ventralizes the embryo.
C) BMP function is inhibited by organizer signals
D) BMPs are signaling ligands that bind to cell-surface receptors on target cells.

Question 7

Which of the following is the only structure induced If one performs the organizer transplantation experiment with a blastopore lip from a late stage gastrula?

A) Head
B) Trunk
C) Tail
D) Brain

Question 8

Which of the following is not a secreted organizer protein?

A) Chordin
B) Noggin
C) Follistatin
D) BMP

Question 9

Transplanting a piece of anterior mesoderm to the blastocoel of a host frog embryo will induce which of the following structures?

A) Head
B) Trunk
C) Tail
D) Spinal cord

Question 10

In the zebrafish embryo, what is the equivalent of the Xenopus organizer?

A) Shield
B) Node
C) Blastopore lip
D) Plate