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Question 1

Epimorphosis is regeneration through:

a) repatterning of existing cells, as occurs in Hydra.

b) the reinitiation of division in existing cells, followed by patterning, as occurs in Hydra.

c) the reinitiation of division in existing cells, followed by patterning, as occurs in amphibians such as newts.

d) repatterning of existing cells, as occurs in amphibians.

e) reinitiation of embryonic growth from the remaining cells, as occurs in Hydra.

Question 2

When the blastema forms after amputation of a newt limb, what processes must the cells undergo in order for regeneration to occur?

a) The cells must only begin to divide for regeneration to occur.

b) The cells must simply dedifferentiate in order for regeneration to occur.

c) The overlying wound epidermis takes on a role similar to that of the apical ectodermal ridge in normal limb development, and limb regeneration can then occur.

d) Some cells in the blastema will transdifferentiate after amputation, and this allows regeneration to proceed.

e) Dedifferentiation, cell division, transdifferentiation, and formation of an AER-like function are all involved.

Question 3

If the nerve supply to a newt limb is severed before amputation, how will this affect regeneration?

a) It will have no effect, since regeneration involves growth of new muscle, bone, and connective tissue.

b) Regeneration of most tissues will occur normally, but regeneration of the nerves will not occur.

c) Outgrowth will occur, but the identity of the limb will be lost and normal proximo-distal patterning will not occur.

d) A blastema will form but will not grow, and regeneration will fail.

e) ANo regeneration occurs, and the stump heals over as it would in a mammal.

Question 4

"Intercalary growth" in a regenerating amphibian limb means that if a distal blastema is grafted to a proximal stump:

a) the distal blastema grows back, to regenerate proximal elements, then out, to regenerate distal structures.

b) the stump grows out to regenerate proximal structures, until the positional values of the blastema are produced, at which time the distal blastema takes over and completes outgrowth of distal structures.

c) the distal blastema grows out, regenerating distal structures, resulting in a limb lacking intermediate structures.

d) the distal blastema grows proximally, intercalating intermediate structures between it and the stump, then growth stops, resulting in a regenerate lacking distal structures.

e) the stump grows out, intercalating intermediate structures between it and the distal blastema, then growth stops, resulting in a regenerate lacking distal structures.

Question 5

How does the dose-dependence of retinoic acid treatment support the notion that a gradient of retinoic acid can act as a morphogen along the proximo-distal axis in the limb?

a) Treatment with high levels of retinoic acid causes a proximal blastema to be respecified as a distal blastema, and only distal structures are regenerated.

b) Treatment with high levels of retinoic acid causes any blastema to form only distal structures.

c) Treatment with high levels of retinoic acid causes any blastema to be respecified as a proximal blastema, but it will form only proximal structures.

d) Treatment with high levels of retinoic acid causes a distal blastema to be respecified as a proximal blastema, and regeneration of a full limb may be initiated from proximal values.

e) Treatment with retinoic acid affects only distal blastemas, and causes them to form only proximal structures.

Question 6

What is especially exciting about research into regeneration in zebrafish?

a) Amputation of a fin leads to regeneration of a limb, implying an evolutionary homology between the two structures.

b) Removal of the eye results in regeneration of the eye, and since zebrafish and humans have very similar eyes, this research may lead to new therapies for eye damage in humans.

c) Limited regeneration of heart muscle can occur in zebrafish, and the ability to study zebrafish genetically will enhance our ability to understand the genetic basis of regeneration.

d) Regeneration of the heart muscle does not occur in either humans or zebrafish, but experiments can be done on zebrafish that cannot be done on humans, opening up a model system in which to study heart regeneration for use in humans.

e) Mutations have been found that enhance the regenerative powers of zebrafish, and it is hoped that the genes found can be exploited in enhancing human regeneration.

Question 7

Which statement correctly characterizes regeneration in the mammalian nervous system?

a) In some instances, peripheral nerves can regenerate an axon if cut, such as when motor neurons regenerate axons to make correct connections with muscles.

b) Killed cells of the peripheral nervous system can be regenerated and will extend axons to restore connectivity with targets.

c) Cells of the brain can regenerate if damaged, but the peripheral nervous system is incapable of regeneration.

d) Fully functional regeneration in the mammalian nervous system has been shown to be possible when adult stem cell transplants are used.

e) The glial cells of the central nervous system support axon outgrowth and regeneration, but the glial cells of the peripheral nervous system seem to actually suppress nerve regeneration.

Question 8

Is regeneration in Hydra similar to regeneration in vertebrates, or is it fundamentally different in some way?

a) Regeneration in Hydra occurs through a repatterning of existing cells by morphallaxis, unlike regeneration in vertebrates, which occurs through epimorphosis.

b) Regeneration in Hydra occurs through the reinitiation of cell division in existing cells, followed by repatterning of those cells, very much like regeneration in vertebrates.

c) Regeneration in Hydra occurs through the reinitiation of cell division in existing cells, followed by repatterning of those cells, which is totally different from regeneration in vertebrates.

d) Regeneration in Hydra occurs through the reinitiation of cell division in existing cells, followed by repatterning of those cells, whereas regeneration in vertebrates occurs through a process of repatterning of existing cells.

e) Regeneration in Hydra occurs through the reinitiation of embryonic growth and patterning, in contrast to regeneration in vertebrates which occurs through a process of epimorphosis.

Question 9

We learned in Chapter 3 (page 114) that treatment of Xenopus embryos with lithium dorsalizes the embryos by interfering with cell-cell signaling pathways. What, if anything, is the effect of lithium on Hydra, and what might we infer about its mechanism of action?

a) Lithium has no effect in Hydra.

b) Lithium dorsalizes Hydra just as it does Xenopus, so we would assume its mechanism of action is identical in the two organisms.

c) Lithium causes the formation of extra basal discs, which we might infer arise through interference with cell-cell signaling pathways.

d) Lithium causes the formation of extra head regions, since the head of Hydra is mechanistically analogous to the dorsal side of Xenopus embryos.

e) Lithium leads to the formation of extra head regions, since lithium blocks GSK-3 and thus β-catenin degradation, and high β-catenin levels are found in the Hydra head region.

Question 10

What molecular marker of head identity is found in the apical tip of a Hydra during head regeneration?

a) Hox genes from the 3'(anterior) end of the Hydra Hox complex.

b) A bud characteristic of the budding region.

c) BMPs

d) Nodal

e) Wnt

Oxford University Press, Online Resource Centre, Chapter 13.

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