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Question 1

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?

a) Previously, we have studied only gene expression patterns, whereas now we are concerned with cell-cell signaling as well.

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

c) 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.

d) 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.

e) There is no fundamental difference in mechanism between patterning events such as axis formation and morphogenic events such as gastrulation.

Question 2

Adherens junctions play in important role in development; they are composed of:

a) Cadherins linked to other cadherins extracellularly, and to actin filaments intracellularly.

b) Cadherins linked to other cadherins extracellularly, and to intermediate filaments intracellularly.

c) Immunoglobulin superfamily (IgSF) molecules linked to other IgSF molecules extracellularly, and to the cytoskeleton intracellularly.

d) Integrins linked to extracellular matrix molecules extracellularly, and to the cytoskeleton intracellularly.

e) Integrins linked to IgSF molecules extracellularly, and both types of transmembrane molecules linked to the cytoskeleton intracellularly.

Question 3

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

a) The cells will regulate to form one or more normal embryos.

b) The cells will often sort themselves so that like cells are together.

c) The cells will reaggregate to form a normal embryo capable of continuing development.

d) The cells will associate with one another randomly.

e) The cells will undergo apoptosis, due to their lack of normal cell-cell adhesions.

Question 4

Compare Fig. 3.5 and Fig. 7.4: what type of cleavage is used in frog embryos?

a) radial

b) unequal

c) spiral

d) superficial

e) indeterminate

Question 5

Which of the following is the only true statement regarding compaction in the mouse embryo?

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

b) 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.

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

d) All of the above are true of compaction in the mouse embryo.

e) None of the above is true of compaction in the mouse embryo.

Question 6

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

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

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

c) 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.

d) The crawl inside the blastocoel and form a solid rod, which is then hollowed out to form the tube of the gut.

e) They enter the interior of the embryo through the dorsal lip of the blastopore and, through a combination of cell movements and convergent extension, form the gut.

Question 7

Contrast involution, epiboly, and convergent extension.

a) 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.

b) 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.

c) 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.

d) 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 cove.

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

Question 8

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:

a) ectoderm.

b) mesoderm.

c) endoderm.

d) yolk.

e) neural ectoderm.

Question 9

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:

a) involution.

b) convergent extension.

c) epiboly.

d) invagination.

e) intercalation.

Question 10

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

a) involution.

b) convergent extension.

c) epiboly.

d) invagination.

e) intercalation.

Question 11

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

a) involution.

b) convergent extension.

c) epiboly.

d) invagination.

e) intercalation.

Question 12

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

a) Changes in cell shape in the neural plate are the only process required for neural tube formation.

b) 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.

c) Both 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.

d) Prospective neural tube cells in the ectoderm undergo medio-lateral intercalation, then involute and form the neural tube.

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

Question 13

Neural crest cells will become:

a) Medullary cells of the adrenal gland.

b) Neurons in the sympathetic ganglia of the autonomic nervous system.

c) Neurons in the dorsal root ganglia of the peripheral nervous system.

d) Pigment cells in the dermis.

e) All of the above are derived from neural crest cells.

Question 14

Neural crest cells taking the dorso-lateral route will become:

a) dorsolateral route ganglia.

b) adrenal medulla.

c) sympathetic ganglia.

d) unsympathetic ganglia.

e) melanocytes.

Oxford University Press, Online Resource Centre, Chapter 07.

Chapter 07

Instructions

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14