Transcript 9-Clicker-Questions-Induction

MCDB 4650
Induction and Mesoderm
Patterning
If you isolate animal cap cells from a Xenopus embryo at
the 8-cell stage and assay them 1 day later, they will
not have made mesoderm. If you combine vegetal
cells with animal cells at the same stage and assay
them 1 day later, the animal cells will now have made
mesoderm. This tells you that:
a. the animal cells are committed at the 8-cell stage.
b. the vegetal cells are not committed at the 8-cell stage.
c. the vegetal cells induce the animal cells to make
mesoderm.
d. the animal cells induce the vegetal cells to make
mesoderm.
e. the two sets of cells interact by lateral inhibition.
Which of the following is NOT true of the
organizer?
a. Induces gastrulation
b. Inhibits ventral ectoderm
c. Converts ventral mesoderm to intermediate
mesoderm
d. Involutes through the dorsal lip of the blastopore
e. Becomes intermediate mesoderm
The initial induction of mesoderm is
accomplished by
a. activation of the Wnt pathway
b. activation of the TGFb pathway
c. activation of the Shh pathway
d. activation of the Ras pathway
e. activation of the FGF pathway
The patterning of dorsal mesoderm as different
from ventral mesoderm involves
a. higher concentrations of signaling molecules
on the dorsal side than on the ventral
b. transcription of molecules that can inhibit
molecules present on the ventral side
c. transcription of molecules that direct synthesis
of dorsal-specific proteins
How could you best assay whether the Xnr’s were in a
concentration gradient across the embryo?
a. Grind up different parts of Xenopus embryos and
assay protein level
b. Make embryos mutant for Xnrs and assay the
outcome
c. Transplant the Niewkoop center into a UV irradiated
embryo and assay the outcome
d. Put purified Xnr protein into a bead (from which the
Xnr can diffuse) and put the bead into culture with
animal cap cells. Assay types of cells made
e. Two of the above would work equally well
The organizer induces neural ectoderm by:
a. inhibiting an inhibitor that normally prevents neural fate
b. directly inhibiting epidermal fate
c. activating a neural transcription factor
d. activating b-catenin signaling
e. segregation of neural-specific transcription factors
Mesoderm arises near the equator (in the marginal zone) of the
Xenopus blastula because
a) animal hemisphere cells in this region are autonomously
determined to become mesodermal precursors.
b) vegetal hemisphere cells in this region are autonomously
determined to become mesodermal precursors.
c) animal hemisphere cells in this region receive signals
from underlying vegetal hemisphere cells and become mesodermal
precursors.
d) vegetal hemisphere cells in this region receive signals
from overlying animal hemisphere cells and become mesodermal
precursors.
Activin was postulated as a mesoderm-inducing morphogen
because it
a) was found in the medium after incubation of
animal cap cell cultures.
b) was found in the medium after incubation of
vegetal cell cultures.
c) induced different mesodermal cell types when
incubated at different concentrations with
animal cap cells in culture.
d) induced different mesodermal cell types when
incubated at different concentrations with
vegetal cells in culture.
Which of these statements is true in the Xenopus embryo?
a) The organizer induces formation of neural ectoderm
by locally inhibiting an inhibitor of neural
cell fates in the animal cap.
b) The organizer induces formation of neural ectoderm
by locally inducing animal cap cells that
would otherwise adopt epidermal fates.
c) The organizer moves during gastrulation toward the
future anterior of the body axis and then
retracts again toward the ventral side, leaving
notochord tissue behind it.
d) The organizer cells contain activated -catenin as a
master transcriptional regulator.
e)
The organizer secretes factors that activate formation
of the Nieuwkoop center.