BIOL 331 | ADVANCED
DEVELOPMENTAL BIOLOGY FINAL
EXAM 2026/2027 QUESTIONS &
VERIFIED ANSWERS 2026/2027 UPDATE
1. In Drosophila melanogaster, the maternal gradient of Bicoid protein establishes the
anterior-posterior axis. Which mechanism best describes how Bicoid regulates the translation
of caudal mRNA?
A. Bicoid binds to the 3’ UTR of caudal mRNA and inhibits its translation via the Bicoid-
binding region (BBR).
B. Bicoid binds to the 5’ UTR of caudal mRNA to enhance ribosomal recruitment.
C. Bicoid acts as a transcriptional repressor for the caudal gene in the anterior region.
D. Bicoid recruits Nanos to degrade caudal mRNA in a sequence-specific manner.
Answer: A
Conceptual Explanation: Bicoid protein functions both as a transcription factor for gap
genes and as a translational repressor. It binds to the 3’ UTR of caudal mRNA at the BBR,
preventing its translation in the anterior of the embryo.
,2. During the activation of the Wnt/beta-catenin signaling pathway, what is the specific role
of the protein Dishevelled (Dvl)?
A. It recruits the destruction complex to the plasma membrane, preventing the
phosphorylation of beta-catenin.
B. It acts as a nuclear transcription factor alongside TCF/LEF.
C. It directly phosphorylates beta-catenin for degradation.
D. It cleaves the extracellular domain of the Frizzled receptor.
Answer: A
Conceptual Explanation: Upon Wnt binding to Frizzled/LRP5/6, Dishevelled is activated
and recruits the Axin/GSK3/APC destruction complex to the membrane, which stabilizes
beta-catenin by preventing its degradation.
3. Which transcription factor is considered the ‘master regulator’ of the mammalian SRY-
independent pathway for ovary differentiation?
A. Sox9
B. Fgf9
C. Wnt4
D. Sf1
Answer: C
, Conceptual Explanation: Wnt4, along with R-spondin1, promotes the ovarian pathway by
stabilizing beta-catenin, which inhibits Sox9 and promotes the expression of female-
specific genes.
4. In the ‘Clock and Wavefront’ model of somitogenesis, what molecules typically constitute
the ‘wavefront’?
A. A gradient of FGF8 and Wnt3a
B. Cyclic Hes/Her genes
C. High concentrations of Retinoic Acid
D. Notch delta ligands
Answer: A
Conceptual Explanation: The wavefront is defined by a posterior-to-anterior gradient of
FGF and Wnt signaling, which determines the position where cells become competent to
form a somite boundary.
5. During C. elegans development, the P-granules are restricted to the germline precursor
cells. Which protein is primarily responsible for the posterior localization of P-granules in the
zygote?
A. PAR-1
B. PAR-6
C. PKC-3
DEVELOPMENTAL BIOLOGY FINAL
EXAM 2026/2027 QUESTIONS &
VERIFIED ANSWERS 2026/2027 UPDATE
1. In Drosophila melanogaster, the maternal gradient of Bicoid protein establishes the
anterior-posterior axis. Which mechanism best describes how Bicoid regulates the translation
of caudal mRNA?
A. Bicoid binds to the 3’ UTR of caudal mRNA and inhibits its translation via the Bicoid-
binding region (BBR).
B. Bicoid binds to the 5’ UTR of caudal mRNA to enhance ribosomal recruitment.
C. Bicoid acts as a transcriptional repressor for the caudal gene in the anterior region.
D. Bicoid recruits Nanos to degrade caudal mRNA in a sequence-specific manner.
Answer: A
Conceptual Explanation: Bicoid protein functions both as a transcription factor for gap
genes and as a translational repressor. It binds to the 3’ UTR of caudal mRNA at the BBR,
preventing its translation in the anterior of the embryo.
,2. During the activation of the Wnt/beta-catenin signaling pathway, what is the specific role
of the protein Dishevelled (Dvl)?
A. It recruits the destruction complex to the plasma membrane, preventing the
phosphorylation of beta-catenin.
B. It acts as a nuclear transcription factor alongside TCF/LEF.
C. It directly phosphorylates beta-catenin for degradation.
D. It cleaves the extracellular domain of the Frizzled receptor.
Answer: A
Conceptual Explanation: Upon Wnt binding to Frizzled/LRP5/6, Dishevelled is activated
and recruits the Axin/GSK3/APC destruction complex to the membrane, which stabilizes
beta-catenin by preventing its degradation.
3. Which transcription factor is considered the ‘master regulator’ of the mammalian SRY-
independent pathway for ovary differentiation?
A. Sox9
B. Fgf9
C. Wnt4
D. Sf1
Answer: C
, Conceptual Explanation: Wnt4, along with R-spondin1, promotes the ovarian pathway by
stabilizing beta-catenin, which inhibits Sox9 and promotes the expression of female-
specific genes.
4. In the ‘Clock and Wavefront’ model of somitogenesis, what molecules typically constitute
the ‘wavefront’?
A. A gradient of FGF8 and Wnt3a
B. Cyclic Hes/Her genes
C. High concentrations of Retinoic Acid
D. Notch delta ligands
Answer: A
Conceptual Explanation: The wavefront is defined by a posterior-to-anterior gradient of
FGF and Wnt signaling, which determines the position where cells become competent to
form a somite boundary.
5. During C. elegans development, the P-granules are restricted to the germline precursor
cells. Which protein is primarily responsible for the posterior localization of P-granules in the
zygote?
A. PAR-1
B. PAR-6
C. PKC-3
