BIOL 331: ADVANCED
DEVELOPMENTAL BIOLOGY EXAM 3
QUESTIONS & VERIFIED ANSWERS
2026/2027 UPDATE
1. During primary neurulation, which signaling molecules are secreted by the notochord to
induce the formation of the Medial Hinge Point (MHP)?
A. BMP inhibitors such as Noggin and Chordin
B. Retinoic Acid
C. Wnt7a and FGF8
D. Shh (Sonic Hedgehog)
Answer: D
Conceptual Explanation: The notochord secretes Shh, which induces the overlying
ectoderm to become the floor plate and forms the MHP by triggering apical constriction.
2. Which transcription factor is considered the ‘master regulator’ for eye development,
capable of inducing ectopic eyes when misexpressed?
A. Otx2
B. Pax6
C. Rx1
,D. Sox2
Answer: B
Conceptual Explanation: Pax6 is the master control gene for eye development across
species; its expression is necessary and sufficient for eye formation.
3. In the trunk neural crest, cells following the dorsolateral pathway will eventually become:
A. Sympathetic ganglia
B. Adrenal medullary cells
C. Dorsal root ganglia
D. Melanocytes
Answer: D
Conceptual Explanation: Trunk neural crest cells that migrate dorsolaterally between the
epidermis and the dermis differentiate into melanocytes.
4. The ‘Clock-and-Wavefront’ model of somitogenesis explains the periodicity of somite
formation. What represents the ‘wavefront’ in this model?
A. The oscillating expression of Notch signaling
B. The gradient of FGF8 and Wnt3a
C. The rhythmic activation of Hairy1
D. The concentration of Retinoic Acid in the anterior PSM
, Answer: B
Conceptual Explanation: The wavefront is defined by a posterior-to-anterior gradient of
FGF8 and Wnt3a, which maintains cells in an undifferentiated state until they reach the
determination front.
5. Which mesodermal derivative gives rise to the kidneys and the gonads?
A. Paraxial mesoderm
B. Intermediate mesoderm
C. Lateral plate mesoderm
D. Chordamesoderm
Answer: B
Conceptual Explanation: Intermediate mesoderm is specialized to form the urogenital
system, including the kidneys and genital ducts.
6. During limb development, the Zone of Polarizing Activity (ZPA) is responsible for patterning
which axis?
A. Anteroposterior
B. Proximodistal
C. Dorsoventral
D. Mediolateral
Answer: A
DEVELOPMENTAL BIOLOGY EXAM 3
QUESTIONS & VERIFIED ANSWERS
2026/2027 UPDATE
1. During primary neurulation, which signaling molecules are secreted by the notochord to
induce the formation of the Medial Hinge Point (MHP)?
A. BMP inhibitors such as Noggin and Chordin
B. Retinoic Acid
C. Wnt7a and FGF8
D. Shh (Sonic Hedgehog)
Answer: D
Conceptual Explanation: The notochord secretes Shh, which induces the overlying
ectoderm to become the floor plate and forms the MHP by triggering apical constriction.
2. Which transcription factor is considered the ‘master regulator’ for eye development,
capable of inducing ectopic eyes when misexpressed?
A. Otx2
B. Pax6
C. Rx1
,D. Sox2
Answer: B
Conceptual Explanation: Pax6 is the master control gene for eye development across
species; its expression is necessary and sufficient for eye formation.
3. In the trunk neural crest, cells following the dorsolateral pathway will eventually become:
A. Sympathetic ganglia
B. Adrenal medullary cells
C. Dorsal root ganglia
D. Melanocytes
Answer: D
Conceptual Explanation: Trunk neural crest cells that migrate dorsolaterally between the
epidermis and the dermis differentiate into melanocytes.
4. The ‘Clock-and-Wavefront’ model of somitogenesis explains the periodicity of somite
formation. What represents the ‘wavefront’ in this model?
A. The oscillating expression of Notch signaling
B. The gradient of FGF8 and Wnt3a
C. The rhythmic activation of Hairy1
D. The concentration of Retinoic Acid in the anterior PSM
, Answer: B
Conceptual Explanation: The wavefront is defined by a posterior-to-anterior gradient of
FGF8 and Wnt3a, which maintains cells in an undifferentiated state until they reach the
determination front.
5. Which mesodermal derivative gives rise to the kidneys and the gonads?
A. Paraxial mesoderm
B. Intermediate mesoderm
C. Lateral plate mesoderm
D. Chordamesoderm
Answer: B
Conceptual Explanation: Intermediate mesoderm is specialized to form the urogenital
system, including the kidneys and genital ducts.
6. During limb development, the Zone of Polarizing Activity (ZPA) is responsible for patterning
which axis?
A. Anteroposterior
B. Proximodistal
C. Dorsoventral
D. Mediolateral
Answer: A
