Developmental Signalling and Molecular Embryology (HOX, SHH, Neural Crest) MCQs

Anatomy · 36 free questions with answers & explanations.

1. During limb bud development, the zone of polarizing activity (ZPA) on the posterior mesenchyme of the limb bud secretes a morphogen that patterns the anterior-posterior axis. This morphogen is:
2. Neural crest cells that migrate from the rhombencephalon to populate pharyngeal arch 1 give rise to all of the following EXCEPT:
3. During spinal cord development, ventral horn motor neurones are specified by the transcription factor Olig2 in response to a ventral-to-dorsal gradient of which signalling molecule secreted by the notochord and floor plate?
4. A mutation disrupting HOX gene expression specifically affects segmental identity of vertebrae. Thoracic vertebrae 'transformed' into cervical identity (homeotic transformation) would most likely result from a mutation in which class of genes?
5. Sonic Hedgehog (SHH) is secreted from the zone of polarizing activity (ZPA) of the limb bud. Loss-of-function mutations in SHH cause which specific limb anomaly?
6. HOX gene clusters A–D are expressed along the craniocaudal axis. Which principle best explains the phenotypic consequence of mutations in posterior HOX genes?
7. A newborn presents with conotruncal heart defect (persistent truncus arteriosus), absent thymus, hypocalcaemia, and abnormal facial features. Failure of migration of neural crest cells from which rhombomeric level primarily accounts for the cardiovascular defect?
8. Wnt/β-catenin signalling in the developing kidney is critical for ureteric bud branching morphogenesis. A mutation blocking Wnt9b specifically disrupts:
9. Sonic Hedgehog (SHH) secreted from the zone of polarizing activity (ZPA) in the developing limb bud establishes which pattern?
10. Neural crest cells migrating from which axial level give rise to the enamel organ and dentine-forming odontoblasts of the teeth?
11. HOX gene mutations are associated with limb malformations in humans. Which general principle governs HOX gene expression in the vertebral column?
12. The cardiac neural crest cells are required for normal cardiovascular development. Ablation of cardiac neural crest results in which specific defect?
13. Mutations in the HOXA13 gene cause hand-foot-genital syndrome. Which developmental principle does this best illustrate?
14. Sonic Hedgehog (SHH) signalling from the notochord is required for floor plate induction and ventral neural tube patterning. Inactivation of SHH in the notochord leads to absence of which spinal cord neuron population?
15. DiGeorge syndrome results from failure of neural crest cell migration into the third and fourth pharyngeal pouches. Which structure is NOT derived from neural crest-populating pharyngeal arch derivatives?
16. Hirschsprung disease (congenital aganglionosis of the distal colon) results from failure of which cell population to colonise the developing hindgut?
17. The apical ectodermal ridge (AER) of the developing limb bud is maintained by a reciprocal signalling loop. Which factor from the underlying mesenchyme maintains AER integrity?
18. Sonic Hedgehog (SHH) protein, secreted from the zone of polarizing activity (ZPA) of the developing limb bud, establishes the anteroposterior axis. When SHH signalling is experimentally duplicated on the anterior margin of the chick wing bud, the result is:
19. Neural crest cells that migrate from the post-otic rhombomeres (r6–r8) contribute to which of the following structures?
20. HOX gene expression along the craniocaudal axis of the embryo follows the colinearity principle. Which statement correctly describes this principle?
21. A fetus is found to have absence of the dorsal pancreatic bud derivatives. Which transcription factor mutation is most likely responsible?
22. During limb development, Sonic Hedgehog (SHH) is secreted from the Zone of Polarizing Activity (ZPA). What is the primary role of this signalling gradient in limb patterning?
23. Neural crest cells originating from the rhombencephalic segments (rhombomeres 1 and 2) migrate into which pharyngeal arch and give rise to which skeletal elements?
24. During neural tube closure, PAX3 and PAX7 are expressed in the dorsal neural tube while NKX2.2 and OLIG2 are expressed ventrally. Which signalling molecule establishes this dorsoventral pattern by inducing ventral progenitor identities?
25. A newborn is found to have absent thymus and parathyroid glands with a conotruncal cardiac defect (truncus arteriosus) and a characteristic facial dysmorphism. Absence of migration of neural crest cells from which region is responsible?
26. Sonic hedgehog (SHH) protein secreted by the zone of polarizing activity (ZPA) of the developing limb bud controls which aspect of limb patterning?
27. A newborn presents with absent thymus and parathyroid glands, conotruncal cardiac defect, and hypocalcemia. The embryological structure most responsible for this syndrome is:
28. During cardiac development, the primitive interventricular foramen (IVF) is closed primarily by fusion of which three structures?
29. HOX gene expression along the craniocaudal axis follows collinearity. Which statement best describes spatial collinearity of HOX genes?
30. Sonic Hedgehog (SHH) is secreted from the zone of polarizing activity (ZPA) in the developing limb bud. Its primary function is:
31. Neural crest cells are pluripotent migratory cells derived from the dorsal neural tube. Which of the following is NOT a neural crest derivative?
32. Sonic Hedgehog (SHH) protein is secreted from the zone of polarizing activity (ZPA) in the developing limb bud. Its primary role is to determine:
33. Neural crest cells that migrate from the rhombomeres of the hindbrain contribute to the formation of:
34. HOX gene clusters provide positional identity along the cranio-caudal axis. Loss-of-function mutations in HOX genes typically produce:
35. During cardiogenesis, the primary heart tube is initially formed by which embryonic structure?
36. The notochord plays a critical signaling role in early development. After its inductive function is complete, it persists in the adult as which structure?