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. Previous chapters have focused on the establishment of embryonic axes and the specification of cellular identity. At the molecular and cellular level, how does morphogenesis differ from those processes?

Previously, we have studied only gene-expression patterns, whereas now we are concerned with cell-cell signaling as well correct incorrect

Previously, cell-cell signaling has been the major focus, whereas in morphogenesis we will be concerned with gene expression primarily. correct incorrect

The specification of pattern and fate has been presented as being completely under maternal control, whereas now we are concerned with zygotic control over development. correct incorrect

The formation of embryonic axes and the specification of cell fates rely heavily on cell-cell signaling events, and their influence over gene-expression patterns, whereas morphogenesis relies primarily on cell-cell adhesion and cell motility. correct incorrect

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. Adherens junctions have an important role in development; they are composed of

cadherins linked to other cadherins extracellularly, and to actin filaments intracellularly correct incorrect

cadherins linked to other cadherins extracellularly, and to intermediate filaments intracellularly correct incorrect

immunoglobulin superfamily (IgSF) molecules linked to other IgSF molecules extracellularly, and to the cytoskeleton intracellularly correct incorrect

integrins linked to extracellular matrix molecules extracellularly, and to the cytoskeleton intracellularly correct incorrect

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. If embryos are disaggregated with chemicals or proteases, and the individual cells are mixed together in culture, what will happen?

The cells will associate with one another randomly. correct incorrect

The cells will often sort themselves so that cells of the same type are together. correct incorrect

The cells will reaggregate to form a normal embryo capable of continuing development. correct incorrect

The cells will regulate to form one or more normal embryos. correct incorrect

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. What type of cleavage is used in frog embryos?

radial correct incorrect

spiral correct incorrect

superficial correct incorrect

unequal correct incorrect

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. Which of the following statements best describes compaction in the mouse embryo?

Compaction involves the activation of cadherins, resulting in an increase in cell-cell adhesion among the 8 cells of the embryo. correct incorrect

Compaction involves a polarization of the cells of the embryo, such that ions can be pumped from the outer surface of the embryo into the central cavity, resulting in an influx of water into the central cavity and formation of the blastocoel. correct incorrect

Compaction gives subsequent cell divisions an orientation, such that cell divisions that occur tangential (parallel) to the cell surface will result in one daughter cell being inside the embryo, where it can contribute to the inner cell mass. correct incorrect

All the options given are true of compaction in the mouse embryo. correct incorrect

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. How do the endodermal cells of the sea urchin embryo carry out gut formation during gastrulation?

Changes in cell shape initiate the invagination; convergent extension extends the sheet of cells into the blastocoel, and finally, filopodia make contact with the future mouth region and pull the tip of the gut to that point. correct incorrect

They crawl inside the blastocoel and form a solid rod, which is then hollowed out to form the tube of the gut. correct incorrect

They move inside the blastocoel, and form the skeletal structures that will support the adult animal. correct incorrect

They move into the blastocoel as mesenchyme and crawl ventrally, to mark the location of the future mouth. correct incorrect

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. Gastrulation in sea urchins, Drosophila, and Xenopus all begin with a change in cell shape, in which the apical surface of an epithelial sheet contracts. This process is called

convergent extension correct incorrect

epiboly correct incorrect

invagination correct incorrect

involution correct incorrect

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. A fate map of a Xenopus blastula, just before gastrulation begins, shows (Figure 4.8) that the top portion of the embryo will become ectoderm (skin and nerve), the central portion will become mesoderm (bone, muscle, and blood), and the lowest portion will become endoderm (gut). How is it that the endoderm and mesoderm, shown on the outside in the fate map, end up on the inside in the embryo after gastrulation?

The endoderm ends up inside through a process that can be visualized as if one pokes their finger into the bottom of a soft ball until the lowest endodermal portion ends up deep inside, the marginal zone mesoderm also ends up inside, and the ectoderm now encloses the entire outer surface. correct incorrect

The endodermal cells begin first to move into the embryo through the blastopore, displacing the blastocoel and forming a gut; as gastrulation proceeds, the blastopore spreads sideways and the mesoderm follows the endoderm in, ending up between the endoderm and the ectoderm. correct incorrect

The ectodermal cells divide and spread down over the rest of the embryo, so that the endoderm ends up on the bottom, ventral, surface of the embryo, and the mesoderm ends up around the middle, just as is shown in the fate map. correct incorrect

The cells, having already been fated to form endoderm and mesoderm, migrate directly into the interior of the embryo and take up residence in appropriate places. correct incorrect

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. During gastrulation in the frog, the very first cells to move into the interior of the embryo through the blastopore come from the surface layer of cells in the marginal zone; they will become:

ectoderm correct incorrect

endoderm correct incorrect

mesoderm correct incorrect

yolk correct incorrect

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. In Xenopus, the mesoderm moves in through the blastopore by rolling around the dorsal lip in a process called

convergent extension correct incorrect

epiboly correct incorrect

invagination correct incorrect

involution correct incorrect

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. In Xenopus, the elongation of the mesoderm toward the anterior results from the intercalation of cells during a process called:

involution correct incorrect

convergent extension correct incorrect

epiboly correct incorrect

invagination correct incorrect

intercalation correct incorrect

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. Contrast involution, epiboly, and convergent extension.

Involution is the movement of cells toward an axis to extend that axis, epiboly is a flattening and spreading of epithelial cells to increase the amount of surface they cover, and convergent extension is the movement of cells inside the embryo as a coherent sheet. correct incorrect

Involution is the movement of cells inside the embryo as a coherent sheet, epiboly is a flattening and spreading of epithelial cells to increase the amount of surface they cover, and convergent extension is movement of cells toward an axis to extend that axis. correct incorrect

Involution is a flattening of epithelial cells to increase the amount of surface they cover, epiboly is the movement of cells inside the embryo as a coherent sheet, and convergent extension is movement of cells toward an axis to extend that axis. correct incorrect

Involution is the movement of cells inside the embryo as a coherent sheet, epiboly is movement of cells toward an axis to extend that axis, and convergent extension is a flattening and spreading of epithelial cells to increase the amount of surface they cover. correct incorrect

* not completed

. In chicks, the formation of the neural tube relies on what cell-biological processes?

Changes in adhesiveness between the prospective neural tube cells and the prospective epidermis in the ectoderm are the only changes required for neural tube formation. correct incorrect

Changes in cell shape in the neural plate and changes in adhesion-molecule expression in the neural tube are required during formation of the neural tube. correct incorrect

Changes in cell shape in the neural plate are the only process required for neural tube formation. correct incorrect

Neural tube formation is a passive by-product of convergent extension in the notochord. correct incorrect

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. Which of the following statements regarding Eph receptors and their ephrin ligands is NOT true:

They act through direct cell-cell contact correct incorrect

Eph receptors are tyrosine kinases correct incorrect

Low levels of kinase activity of Eph receptor results in repulsion correct incorrect

The Eph receptor-ligand interaction can result in repulsion or cell-cell adhesion correct incorrect

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. The development of drugs to block the activity of vascular endothelial growth factor (VEGF) has been applied to the control of the growth of cancers. What is the rationale for such a strategy?

VEGF acts as a growth factor to stimulate the growth of many solid tumors. correct incorrect

Tumor cells produce VEGF to stimulate angiogenesis in their vicinity, and tumors cannot continue to grow without this supply of blood. correct incorrect

Blocking VEGF prevents vasculogenesis in the embryo, and if done properly prevents cancer later in life. correct incorrect

VEGF causes blood vessels to grow toward cancers, which kills the cancer due to too much blood. correct incorrect

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. Neural crest cells will become:

medullary cells of the adrenal gland correct incorrect

neurons in the sympathetic ganglia of the autonomic nervous system correct incorrect

pigment cells in the dermis correct incorrect

all of the options given are derived from neural crest cells correct incorrect

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. Neural crest cells taking the dorsal-lateral route will become

adrenal medulla correct incorrect

dorsal root ganglia correct incorrect

melanocytes correct incorrect

sympathetic ganglia correct incorrect