NYUCD GENERAL EMBRYOLOGY TEST CURRENT
UPDATED - 150 Questions
This exam assesses advanced understanding of gametogenesis and fertilization, covering molecular mechanisms,
genetic regulation, and clinical implications. Questions require synthesis of cellular biology, genetics, and
developmental processes. It contains 150 multiple-choice questions, each with four distractors and a fully worked
rationale that explains why the keyed answer is correct. Content is organized into 12 focused sections:
Gametogenesis and Fertilization, Cleavage and Blastocyst Formation, Implantation and Placenta Formation,
Gastrulation and Germ Layer Formation, Neurulation and Neural Tube Development, Pharyngeal Arches and
Face Development, Cardiovascular System Development, Gastrointestinal and Respiratory System Development,
Urogenital System Development, Limb Development, Fetal Membranes and Twinning, Congenital Anomalies and
Teratology. Targeted learning outcomes include: Analyze the molecular and cellular events of oogenesis and
spermatogenesis; Evaluate the mechanisms of fertilization and early embryonic development; Integrate genetic
and epigenetic factors in gamete formation and fertilization. Every item has been reviewed for clinical accuracy,
current guidelines, and clarity so that students can study with confidence and self-correct as they work through
the bank. Use it as a high-yield review immediately before the exam, or as a structured practice tool during the
unit - the rationales double as concise teaching notes. The recommended writing time is 3 hours, with a passing
score of 80%. Aligned with Conforms to US university standards for graduate-level embryology courses standards
Section 1: Gametogenesis and Fertilization (Questions 1-13)
1 A mutation in the gene encoding zona pellucida glycoprotein ZP2 results in a
truncated protein lacking the cleavage site for ovastacin. Which fertilization
event is most likely impaired?
A) Sperm binding to the zona pellucida
B) Acrosome reaction initiation
C) Block to polyspermy after cortical granule exocytosis
D) Sperm-egg fusion
Answer: C
Rationale: ZP2 cleavage by ovastacin is essential for the zona reaction, which
hardens the zona pellucida and prevents additional sperm binding. Without
cleavage, the block to polyspermy fails, leading to polyspermic fertilization.
2 During oogenesis, the primary oocyte is arrested at diplotene stage of
prophase I until ovulation. Which molecular mechanism maintains this
arrest?
A) High levels of cyclin B and active MPF
B) Phosphorylation and inactivation of MPF by Wee1 kinase
C) Sustained activity of anaphase-promoting complex (APC)
D) Low cAMP levels in the oocyte
,Answer: B
Rationale: Meiotic arrest is maintained by Wee1 kinase-mediated
phosphorylation of CDK1, keeping MPF inactive. High cAMP also contributes
but is not the primary mechanism; APC activity promotes meiosis resumption.
3 A research study identifies a novel sperm-specific isoform of phospholipase
C (PLC) that is essential for initiating calcium oscillations in the egg. Which
event is directly triggered by PLC activity?
A) Completion of meiosis II in the oocyte
B) Cortical granule exocytosis
C) Decondensation of sperm chromatin
D) Formation of the male pronucleus
Answer: A
Rationale: PLC¶ hydrolyzes PIP2 to IP3, causing calcium release from ER
stores. Calcium oscillations activate calmodulin-dependent kinase II, which
inactivates MPF and cytostatic factor, allowing completion of meiosis II.
4 In a patient with non-obstructive azoospermia, testicular biopsy shows
spermatogenic arrest at the primary spermatocyte stage. Which chromosomal
pairing event is most likely defective?
A) Synapsis of homologous chromosomes
B) Formation of the synaptonemal complex
C) Recombination nodules assembly
D) Disjunction of homologous chromosomes
Answer: B
Rationale: Arrest at primary spermatocyte stage (prophase I) suggests defective
synapsis. The synaptonemal complex mediates homologous pairing; its
absence causes meiotic arrest. Recombination occurs later, disjunction is in
anaphase I.
5 Which of the following best explains why human oocytes have a high
incidence of aneuploidy compared to sperm?
A) Spermatogenesis undergoes continuous, efficient checkpoints throughout
life
B) Oocytes are arrested for decades in prophase I, increasing susceptibility to
spindle errors
,C) Sperm undergo multiple rounds of recombination that correct errors
D) Oocytes lack a spindle assembly checkpoint
Answer: B
Rationale: Oocytes remain arrested in prophase I for years, and the prolonged
arrest predisposes to degradation of cohesion complexes and spindle defects.
Spermatogenesis is continuous with robust checkpoints, reducing aneuploidy.
6 A researcher treats mouse sperm with an inhibitor of the CatSper channel
before in vitro fertilization. Which step of fertilization is most likely
blocked?
A) Capacitation
B) Hyperactivated motility
C) Acrosome reaction
D) Sperm-egg fusion
Answer: B
Rationale: CatSper channels are calcium-selective and essential for
hyperactivated motility, which enables sperm to penetrate the zona pellucida.
Inhibition does not affect capacitation, acrosome reaction, or fusion directly.
7 A woman undergoing IVF has oocytes that fail to undergo cortical granule
exocytosis after sperm injection. Which protein is most likely deficient?
A) Ovastacin
B) ZP2
C) Calreticulin
D) Syntaxin-2
Answer: D
Rationale: Cortical granule exocytosis requires SNARE proteins; syntaxin-2 on
the oolemma mediates fusion of cortical granules. Ovastacin is released but is
not required for exocytosis itself; ZP2 is a substrate.
8 Which epigenetic modification is essential for genomic imprinting and
occurs during gametogenesis in a sex-specific manner?
A) Histone acetylation
B) DNA methylation at differentially methylated regions (DMRs)
C) X-chromosome inactivation
D) Polycomb repressive complex binding
, Answer: B
Rationale: Imprints are established by DNA methylation at DMRs during
oogenesis and spermatogenesis, leading to parent-specific expression. Histone
modifications are involved but not the primary imprinting mechanism.
9 A sperm sample shows normal count and motility but fails to fertilize
oocytes in IVF. Further analysis reveals a defect in the acrosome reaction.
Which protein is most likely deficient?
A) Izumo1
B) Fertilin
C) ZP3 receptor
D) ADAM3
Answer: C
Rationale: ZP3 receptor (a protein on the sperm surface) binds ZP3 on the zona
pellucida to trigger the acrosome reaction. Izumo1 and fertilin are involved in
fusion; ADAM3 is important for zona binding but not acrosome reaction.
10 A couple with recurrent pregnancy loss is found to have balanced
translocations in the male partner. Which stage of spermatogenesis is most
affected by this rearrangement?
A) Spermatogonial mitosis
B) Meiotic pairing and recombination
C) Spermiogenesis
D) Spermiation
Answer: B
Rationale: Balanced translocations cause problems during meiotic synapsis and
recombination, leading to unbalanced gametes. Spermatogonial mitosis is
unaffected; spermiogenesis and spermiation are later steps.
11 A spermatozoon undergoes capacitation in the female reproductive tract.
Which molecular change is essential for the acrosome reaction to occur
upon zona pellucida binding?
A) Loss of cholesterol from the plasma membrane and increased membrane
fluidity
B) Hyperpolarization of the sperm membrane potential
C) Phosphorylation of tyrosine residues on the sperm tail
UPDATED - 150 Questions
This exam assesses advanced understanding of gametogenesis and fertilization, covering molecular mechanisms,
genetic regulation, and clinical implications. Questions require synthesis of cellular biology, genetics, and
developmental processes. It contains 150 multiple-choice questions, each with four distractors and a fully worked
rationale that explains why the keyed answer is correct. Content is organized into 12 focused sections:
Gametogenesis and Fertilization, Cleavage and Blastocyst Formation, Implantation and Placenta Formation,
Gastrulation and Germ Layer Formation, Neurulation and Neural Tube Development, Pharyngeal Arches and
Face Development, Cardiovascular System Development, Gastrointestinal and Respiratory System Development,
Urogenital System Development, Limb Development, Fetal Membranes and Twinning, Congenital Anomalies and
Teratology. Targeted learning outcomes include: Analyze the molecular and cellular events of oogenesis and
spermatogenesis; Evaluate the mechanisms of fertilization and early embryonic development; Integrate genetic
and epigenetic factors in gamete formation and fertilization. Every item has been reviewed for clinical accuracy,
current guidelines, and clarity so that students can study with confidence and self-correct as they work through
the bank. Use it as a high-yield review immediately before the exam, or as a structured practice tool during the
unit - the rationales double as concise teaching notes. The recommended writing time is 3 hours, with a passing
score of 80%. Aligned with Conforms to US university standards for graduate-level embryology courses standards
Section 1: Gametogenesis and Fertilization (Questions 1-13)
1 A mutation in the gene encoding zona pellucida glycoprotein ZP2 results in a
truncated protein lacking the cleavage site for ovastacin. Which fertilization
event is most likely impaired?
A) Sperm binding to the zona pellucida
B) Acrosome reaction initiation
C) Block to polyspermy after cortical granule exocytosis
D) Sperm-egg fusion
Answer: C
Rationale: ZP2 cleavage by ovastacin is essential for the zona reaction, which
hardens the zona pellucida and prevents additional sperm binding. Without
cleavage, the block to polyspermy fails, leading to polyspermic fertilization.
2 During oogenesis, the primary oocyte is arrested at diplotene stage of
prophase I until ovulation. Which molecular mechanism maintains this
arrest?
A) High levels of cyclin B and active MPF
B) Phosphorylation and inactivation of MPF by Wee1 kinase
C) Sustained activity of anaphase-promoting complex (APC)
D) Low cAMP levels in the oocyte
,Answer: B
Rationale: Meiotic arrest is maintained by Wee1 kinase-mediated
phosphorylation of CDK1, keeping MPF inactive. High cAMP also contributes
but is not the primary mechanism; APC activity promotes meiosis resumption.
3 A research study identifies a novel sperm-specific isoform of phospholipase
C (PLC) that is essential for initiating calcium oscillations in the egg. Which
event is directly triggered by PLC activity?
A) Completion of meiosis II in the oocyte
B) Cortical granule exocytosis
C) Decondensation of sperm chromatin
D) Formation of the male pronucleus
Answer: A
Rationale: PLC¶ hydrolyzes PIP2 to IP3, causing calcium release from ER
stores. Calcium oscillations activate calmodulin-dependent kinase II, which
inactivates MPF and cytostatic factor, allowing completion of meiosis II.
4 In a patient with non-obstructive azoospermia, testicular biopsy shows
spermatogenic arrest at the primary spermatocyte stage. Which chromosomal
pairing event is most likely defective?
A) Synapsis of homologous chromosomes
B) Formation of the synaptonemal complex
C) Recombination nodules assembly
D) Disjunction of homologous chromosomes
Answer: B
Rationale: Arrest at primary spermatocyte stage (prophase I) suggests defective
synapsis. The synaptonemal complex mediates homologous pairing; its
absence causes meiotic arrest. Recombination occurs later, disjunction is in
anaphase I.
5 Which of the following best explains why human oocytes have a high
incidence of aneuploidy compared to sperm?
A) Spermatogenesis undergoes continuous, efficient checkpoints throughout
life
B) Oocytes are arrested for decades in prophase I, increasing susceptibility to
spindle errors
,C) Sperm undergo multiple rounds of recombination that correct errors
D) Oocytes lack a spindle assembly checkpoint
Answer: B
Rationale: Oocytes remain arrested in prophase I for years, and the prolonged
arrest predisposes to degradation of cohesion complexes and spindle defects.
Spermatogenesis is continuous with robust checkpoints, reducing aneuploidy.
6 A researcher treats mouse sperm with an inhibitor of the CatSper channel
before in vitro fertilization. Which step of fertilization is most likely
blocked?
A) Capacitation
B) Hyperactivated motility
C) Acrosome reaction
D) Sperm-egg fusion
Answer: B
Rationale: CatSper channels are calcium-selective and essential for
hyperactivated motility, which enables sperm to penetrate the zona pellucida.
Inhibition does not affect capacitation, acrosome reaction, or fusion directly.
7 A woman undergoing IVF has oocytes that fail to undergo cortical granule
exocytosis after sperm injection. Which protein is most likely deficient?
A) Ovastacin
B) ZP2
C) Calreticulin
D) Syntaxin-2
Answer: D
Rationale: Cortical granule exocytosis requires SNARE proteins; syntaxin-2 on
the oolemma mediates fusion of cortical granules. Ovastacin is released but is
not required for exocytosis itself; ZP2 is a substrate.
8 Which epigenetic modification is essential for genomic imprinting and
occurs during gametogenesis in a sex-specific manner?
A) Histone acetylation
B) DNA methylation at differentially methylated regions (DMRs)
C) X-chromosome inactivation
D) Polycomb repressive complex binding
, Answer: B
Rationale: Imprints are established by DNA methylation at DMRs during
oogenesis and spermatogenesis, leading to parent-specific expression. Histone
modifications are involved but not the primary imprinting mechanism.
9 A sperm sample shows normal count and motility but fails to fertilize
oocytes in IVF. Further analysis reveals a defect in the acrosome reaction.
Which protein is most likely deficient?
A) Izumo1
B) Fertilin
C) ZP3 receptor
D) ADAM3
Answer: C
Rationale: ZP3 receptor (a protein on the sperm surface) binds ZP3 on the zona
pellucida to trigger the acrosome reaction. Izumo1 and fertilin are involved in
fusion; ADAM3 is important for zona binding but not acrosome reaction.
10 A couple with recurrent pregnancy loss is found to have balanced
translocations in the male partner. Which stage of spermatogenesis is most
affected by this rearrangement?
A) Spermatogonial mitosis
B) Meiotic pairing and recombination
C) Spermiogenesis
D) Spermiation
Answer: B
Rationale: Balanced translocations cause problems during meiotic synapsis and
recombination, leading to unbalanced gametes. Spermatogonial mitosis is
unaffected; spermiogenesis and spermiation are later steps.
11 A spermatozoon undergoes capacitation in the female reproductive tract.
Which molecular change is essential for the acrosome reaction to occur
upon zona pellucida binding?
A) Loss of cholesterol from the plasma membrane and increased membrane
fluidity
B) Hyperpolarization of the sperm membrane potential
C) Phosphorylation of tyrosine residues on the sperm tail
