Skip to main content
Register/ Log In
Register/ Log In
Art and Architecture
Biology and Life Sciences
Communication, Media Studies, & Journalism
Earth and Environmental Science
Women's, Gender & Sexuality Studies
Return to Principles of Development 6e Student Resources
Chapter 7 Self-test questions
Morphogenesis: change in form in the early embryo
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
Previously, cell-cell signaling has been the major focus, whereas in morphogenesis we will be concerned with gene expression primarily.
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.
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.
Adherens junctions have an important role in development; they are composed of
cadherins linked to other cadherins extracellularly, and to actin filaments intracellularly
cadherins linked to other cadherins extracellularly, and to intermediate filaments intracellularly
immunoglobulin superfamily (IgSF) molecules linked to other IgSF molecules extracellularly, and to the cytoskeleton intracellularly
integrins linked to extracellular matrix molecules extracellularly, and to the cytoskeleton intracellularly
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.
The cells will often sort themselves so that cells of the same type are together.
The cells will reaggregate to form a normal embryo capable of continuing development.
The cells will regulate to form one or more normal embryos.
What type of cleavage is used in frog embryos?
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.
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.
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.
All the options given are true of compaction in the mouse embryo.
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.
They crawl inside the blastocoel and form a solid rod, which is then hollowed out to form the tube of the gut.
They move inside the blastocoel, and form the skeletal structures that will support the adult animal.
They move into the blastocoel as mesenchyme and crawl ventrally, to mark the location of the future mouth.
Gastrulation in sea urchins,
all begin with a change in cell shape, in which the apical surface of an epithelial sheet contracts. This process is called
A fate map of a
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.
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.
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.
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.
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:
, the mesoderm moves in through the blastopore by rolling around the dorsal lip in a process called
, the elongation of the mesoderm toward the anterior results from the intercalation of cells during a process called:
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.
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.
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.
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.
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.
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.
Changes in cell shape in the neural plate are the only process required for neural tube formation.
Neural tube formation is a passive by-product of convergent extension in the notochord.
Which of the following statements regarding Eph receptors and their ephrin ligands is NOT true:
They act through direct cell-cell contact
Eph receptors are tyrosine kinases
Low levels of kinase activity of Eph receptor results in repulsion
The Eph receptor-ligand interaction can result in repulsion or cell-cell adhesion
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.
Tumor cells produce VEGF to stimulate angiogenesis in their vicinity, and tumors cannot continue to grow without this supply of blood.
Blocking VEGF prevents vasculogenesis in the embryo, and if done properly prevents cancer later in life.
VEGF causes blood vessels to grow toward cancers, which kills the cancer due to too much blood.
Neural crest cells will become:
medullary cells of the adrenal gland
neurons in the sympathetic ganglia of the autonomic nervous system
pigment cells in the dermis
all of the options given are derived from neural crest cells
Neural crest cells taking the dorsal-lateral route will become
dorsal root ganglia
Select your Country