* not completed

. Maternal factors are

the energy-rich yolk present in the eggs of many species correct incorrect

the genes contributed to the embryo by the maternal haploid genome correct incorrect

the genes expressed by the zygotic genome in the egg correct incorrect

developmentally active mRNAs and proteins packaged into the egg by the mother correct incorrect

* not completed

. Vg-1, Nodals, BMPs and Activin are all members of which family of signaling molecules?

FGF correct incorrect

Hedgehog correct incorrect

TGF-β correct incorrect

Wnt correct incorrect

* not completed

. The role of maternal factors (such as Vg-1, Wnt-11, and VegT) packaged into the vegetal region of the Xenopus oocyte is:

in establishing the future dorso-ventral body axis. correct incorrect

to allow the vegetal region to divide during cleavage. correct incorrect

to specify the future animal-vegetal body axis. correct incorrect

to provide energy and nutrients for the developing embryo. correct incorrect

* not completed

. Between fertilization and the first cleavage division, actin filaments pull the cytoplasm of the frog egg toward the point of sperm entry in a process called:

cortical rotation correct incorrect

dorsalization correct incorrect

blastulation correct incorrect

gastrulation correct incorrect

* not completed

. A key factor that specifies the organizer in Xenopus embryos is:

GSK-3β correct incorrect

Fz7 correct incorrect

Wnt-11 correct incorrect

β-catenin correct incorrect

* not completed

. The nervous system, heart, and liver are derived from _____, _______, and ______, respectively.

all are derived from mesoderm correct incorrect

ectoderm, mesoderm, and endoderm correct incorrect

endoderm, mesoderm, and ectoderm correct incorrect

mesoderm, ectoderm, and endoderm correct incorrect

* not completed

. In frogs, maternal Wnt-11 leads to nuclear localization of _____ in the _____, which in response signals to adjacent cells to become the _____.

β-catenin, Nieuwkoop center, Spemann organizer correct incorrect

nodal, signalling center, shield correct incorrect

Vg-1, vegetal region, Nieuwkoop center correct incorrect

GFP, mesoderm, muscle and bone correct incorrect

* not completed

. If cells from the animal pole of a frog blastula (animal cap cells) are placed into contact with cells from the vegetal hemisphere, after removing the cells fated to form mesoderm, what is the result?

The cells regulate to form a normal embryo. correct incorrect

Animal cap cells are induced to form mesodermal derivatives. correct incorrect

Vegetal hemisphere cells are induced by the animal cap cells to form mesodermal derivatives. correct incorrect

Both animal and vegetal cells lose all specification and an undifferentiated ball of cells results. correct incorrect

* not completed

. Which of the following statements regarding TGF-beta signaling is FALSE?

Type I and Type II receptors form dimers upon ligand binding correct incorrect

Type I receptor is phosphorylated by Type II receptor correct incorrect

Type II receptor determines what types of Smad proteins are activated in the pathway correct incorrect

Activation of Smad proteins 4,5 and 8 induces ventralization of mesoderm correct incorrect

* not completed

. If cells from the animal pole of a Xenopus blastula (animal cap cells) are placed in direct contact with cells from the vegetal region, what is the result?

An embryo forms with only ectodermal and endodermal derivatives. correct incorrect

Animal cap cells are induced by the vegetal cells to form mesodermal derivatives. correct incorrect

The embryo regulates and forms a normal embryo. correct incorrect

Vegetal hemisphere cells are induced by the animal cap cells to form mesodermal derivatives. correct incorrect

* not completed

. The "mid-blastula transition" is the point in development when

translation of maternal mRNA is initiated. correct incorrect

cell determination becomes fixed. correct incorrect

cell division in the embryo ends. correct incorrect

transcription of zygotic genes begins. correct incorrect

* not completed

. What is the mechanism by which cells fated to be mesoderm form in the marginal zone of the Xenopus embryo?

Cells in the marginal zone are fated to be mesoderm, but they do not become specified or determined as mesoderm until after they move internally during gastrulation. correct incorrect

Secreted signals of the TGF- family are released by the cells of the vegetal region and act on the adjacent cells of the marginal zone to instruct them to adopt a mesodermal fate. correct incorrect

Cells of the vegetal region are induced by their proximity to the animal region cells to become mesoderm. correct incorrect

Maternal factors packaged into the marginal zone act on these cells to instruct them to become mesoderm. correct incorrect

* not completed

. The Brachury protein is

expressed early in mesoderm formation correct incorrect

a signaling molecule correct incorrect

expressed throughout the ectoderm correct incorrect

only expressed after gastrulation correct incorrect

* not completed

. The activity of the Chordin protein is

to antagonize BMP signaling and block ventralization of the mesoderm. correct incorrect

to signal through the Chordin pathway and establish the organizer. correct incorrect

to specify a mesodermal fate. correct incorrect

to turn on genes that determine the anterior-most cells in the embryo, which will form the head. correct incorrect

* not completed

. Patterning of the Xenopus mesoderm along the dorso-ventral axis involves an antagonistic relationship between Chordin and BMP-4. Is there an analogy here to dorso-ventral patterning in the Drosophila embryo?

Yes, the Drosophila homolog of BMP-4, Decapentaplegic (Dpp), is antagonized by the Drosophila homolog of Chordin, short gastrulation (Sog), in patterning of the dorso-ventral axis. correct incorrect

Yes, Drosophila also uses BMP-4 to specify ventral fates and chordin to specify dorsal fates. correct incorrect

Yes, the Drosophila Dorsal protein is identical to the vertebrate BMP-4 protein, and specifies the ventral region of the embryo. correct incorrect

No, insect development is totally different than that of real animals like frogs and chickens. correct incorrect

* not completed

. The grafting of the dorsal lip of the blastopore from an early Xenopus gastrula onto the ventral side of another early gastrula will result in

the formation of two separate and independent embryos correct incorrect

the formation of two complete embryos joined along the ventral axis correct incorrect

the formation of two sets of anterior structures joined along the ventral axis: a two-headed embryo correct incorrect

the formation of two sets of posterior structures joined along the ventral axis: a two-tailed embryo correct incorrect

* not completed

. In the early blastula, Wnt signaling and the subsequent nuclear accumulation of β-catenin specifies a dorsal fate, whereas after gastrulation, Wnt/β-catenin signaling specifies

a dorsal fate correct incorrect

a posterior fate correct incorrect

an anterior fate correct incorrect

all of the above correct incorrect

* not completed

. Endoderm and mesoderm are specified in the zebrafish blastoderm by

signals from the shield region correct incorrect

maternal signaling molecules laid down in the egg correct incorrect

a gradient of β-catenin signaling correct incorrect

a gradient of Nodal signaling correct incorrect

* not completed

. In what genetic background could β-catenin turn on target gene expression without the presence of Wnt protein?

Null mutation of GSK-3β correct incorrect

Mutation in APC that fails to form a complex with Axin correct incorrect

Gain-of-function mutation of Frizzled correct incorrect

All of the above correct incorrect