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5.5 Regeneration — Test 1
Q1. Regeneration in which the differentiated cells at a cut surface dedifferentiate to form a blastema that then re-differentiates is called:✓ Epimorphosis
Q2. Regeneration by re-patterning of existing tissues with little new growth is called:✓ Morphallaxis
Q3. Regeneration in which differentiated cells divide while keeping their differentiated state (no blastema) is called:✓ Compensatory regeneration
Q4. Regeneration of the mammalian liver is an example of:✓ Compensatory regeneration
Q5. In Hydra, if a part is lost the remaining tissue re-patterns into a whole animal. This is:✓ Morphallaxis
Q6. Hydra axis formation and head regeneration involve which signalling pathway?✓ Wnt/beta-catenin
Q7. If a transgenic Hydra is made to globally mis-express beta-catenin, the result is:✓ Ectopic buds (and axes) forming along the body
Q8. Planarian (flatworm) regeneration depends on a population of stem cells called:✓ Neoblasts
Q9. Planarian regeneration using neoblasts is best classified as:✓ Stem-cell-mediated regeneration
Q10. In Planaria, the anterior-posterior identity of a regenerating blastema is controlled by the:✓ Wnt pathway (high Wnt = tail; low Wnt = head)
Q11. Amphibian (newt/salamander) limb regeneration occurs through:✓ Formation of a blastema of dedifferentiated cells (epimorphosis)
Q12. Amphibian limb regeneration requires:✓ A minimum number of functional nerves
5.5 Regeneration — Test 2
Q13. If more than 90% of the nerve supply is severed before amputation, newt limb regeneration:✓ Fails (the blastema does not grow despite an apical cap)
Q14. Treating a distal (wrist) newt blastema with a high level of retinoic acid causes it to be:✓ Re-specified as a more proximal blastema, regenerating a more complete limb
Q15. The dedifferentiated cells of a regenerating amphibian limb blastema generally:✓ Retain memory of their tissue of origin (limb cells make limb)
Q16. Zebrafish are notable among vertebrates for being able to regenerate their:✓ Heart (via endogenous cardiac cell proliferation)
Q17. In Hydra, regeneration can occur by:✓ Stem-cell-mediated regeneration, morphallaxis and epimorphosis
Q18. The blastema in epimorphic regeneration consists of:✓ Dedifferentiated, proliferating progenitor cells
Q19. The Wnt inhibitor Notum, expressed at the anterior wound of a regenerating planarian, promotes:✓ Head formation (by lowering Wnt)
Q20. Across these examples, the key difference between morphallaxis and epimorphosis is that morphallaxis:✓ Re-patterns existing tissue with little new growth, while epimorphosis uses a proliferating blastema
Q21. After amphibian limb amputation, the first event is the formation of a wound epidermis that thickens into the:✓ Apical epithelial cap (AEC)
Q22. The apical epithelial cap (AEC) of a regenerating limb is functionally analogous to which embryonic structure?✓ The apical ectodermal ridge (AER)
Q23. Blastema cells in a regenerating salamander limb arise mainly by:✓ Dedifferentiation of mature cells near the cut surface
5.5 Regeneration — Test 3
Q24. Lineage-tracing studies show that regenerating salamander blastema cells are mostly:✓ Lineage-restricted (muscle makes muscle, cartilage makes cartilage)
Q25. The dependence of limb regeneration on nerves is shown by the fact that a denervated amputated limb:✓ Fails to form a growing blastema
Q26. Retinoic acid can change the proximal-distal outcome of regeneration by re-specifying blastema cells to a more ____ identity.✓ Proximal
Q27. Planaria can regenerate a whole worm from a small fragment because their neoblasts are:✓ Pluripotent adult stem cells (the only dividing cells)
Q28. In planarian regeneration, the Wnt signalling gradient sets head-versus-tail identity such that high Wnt specifies:✓ Tail
Q29. If beta-catenin (Wnt pathway) is knocked down throughout a planarian, amputation tends to produce:✓ Heads at both ends (a two-headed worm)
Q30. Hydra head regeneration is organised by the hypostome, which acts as a head organizer by secreting:✓ Wnt proteins (canonical beta-catenin pathway)
Q31. A transgenic Hydra globally mis-expressing beta-catenin develops ectopic tentacles and axes, demonstrating that:✓ Wnt/beta-catenin is sufficient to organise new body axes
Q32. Why can salamanders regenerate limbs while adult mammals largely cannot, despite sharing many genes?✓ Mammals form a scar instead of a blastema; the regenerative program is not fully activated
Q33. Mammalian digit-tip regeneration (the one limb part mammals can regrow) depends on the presence of the:✓ Nail and its associated signalling (e.g. Wnt) at the tip
Q34. Overall, comparing Hydra, planaria and salamanders shows that regeneration:✓ Uses conserved signalling pathways (Wnt, FGF) re-deployed in different ways