NYUCD General Embryology Test | Latest Update 2026/2027 |
200 Practice Questions and Verified Answers | Complete Q&A
Guide | A+ Graded
SECTION 1: GAMETOGENESIS AND FERTILIZATION (Questions 1–35)
1. A male patient presents with azoospermia due to a mutation in the gene encoding the catalytic
subunit of protein kinase A (PKA). Which step of spermatogenesis is most likely directly impaired?
A) Mitotic proliferation of spermatogonia
B) Meiotic recombination in primary spermatocytes
C) Acrosome formation during spermiogenesis
D) Flagellar assembly in spermatids
Answer: C – Acrosome formation during spermiogenesis.
Rationale: PKA signaling is crucial for acrosome biogenesis during spermiogenesis. Mitotic proliferation
and meiotic recombination rely on different kinases (e.g., CDKs). Flagellar assembly involves
intraflagellar transport proteins, not PKA directly.
2. In a mouse model, deletion of the gene encoding ZP3 results in female infertility. Which step of
fertilization is primarily disrupted?
A) Sperm capacitation in the female tract
B) Acrosome reaction upon zona binding
C) Spermzona pellucida binding
D) Fusion of sperm and oolemma
Answer: C – Spermzona pellucida binding.
Rationale: ZP3 is the primary sperm receptor in the zona pellucida; its absence prevents initial binding.
Capacitation occurs before zona binding, and fusion requires different proteins.
,3. 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) Spermegg fusion
Answer: C – Block to polyspermy after cortical granule exocytosis.
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.
4. During oogenesis, the primary oocyte is arrested at the 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 anaphasepromoting complex (APC)
D) Low cAMP levels in the oocyte
Answer: B – Phosphorylation and inactivation of MPF by Wee1 kinase.
Rationale: Meiotic arrest is maintained by Wee1 kinasemediated phosphorylation of CDK1, keeping MPF
inactive. High cAMP also contributes but is not the primary mechanism.
5. Which of the following is the correct sequence of developmental stages in the pig embryo?
A) Zygote, 2cell, 4cell, 8cell, 16cell, morula, blastocyst, expanded blastocyst, hatched blastocyst
B) Zygote, morula, blastocyst, 2cell, 4cell, 8cell, 16cell
C) Morula, zygote, 2cell, 4cell, 8cell, 16cell, blastocyst
D) 2cell, 4cell, 8cell, zygote, 16cell, morula, blastocyst
Answer: A – Zygote, 2cell, 4cell, 8cell, 16cell, morula, blastocyst, expanded blastocyst, hatched
blastocyst.
,Rationale: This is the correct sequence of embryonic development following fertilization.
6. Which of the following is NOT a germ layer of the embryo?
A) Ectoderm
B) Mesoderm
C) Endoderm
D) Trophoblast
Answer: D – Trophoblast.
Rationale: The three germ layers are ectoderm, mesoderm, and endoderm. The trophoblast is an
extraembryonic tissue that contributes to the placenta.
7. What portion of the blastocyst actually becomes the developing embryo?
A) Trophoblast
B) Inner cell mass
C) Blastocoel
D) Zona pellucida
Answer: B – Inner cell mass.
Rationale: The inner cell mass gives rise to the embryo proper. The trophoblast forms the placenta.
8. Which of the following statements about female and male gametogenesis is incorrect?
A) Male meiosis is completed in days or weeks
B) Female meiosis is delayed for months or years
C) The total number of oocytes is regulated by follicle stimulating hormone
D) Spermatogenesis produces four functional gametes from each primary spermatocyte
Answer: C – The total number of oocytes is regulated by follicle stimulating hormone.
, Rationale: The total number of oocytes is determined before birth and is not regulated by FSH. FSH
stimulates follicular development but does not increase the total oocyte count.
9. Normal fertilization typically occurs in which location?
A) Ovary
B) Uterus
C) Ampulla of the fallopian tube
D) Vagina
Answer: C – Ampulla of the fallopian tube.
Rationale: Fertilization usually occurs in the ampulla (the widest portion) of the fallopian tube.
10. Upon entering the vagina, spermatozoa have up to how many days to fertilize the oocyte?
A) 1 day
B) 2 days
C) 4 days
D) 7 days
Answer: C – 4 days.
Rationale: Spermatozoa can survive in the female reproductive tract for up to 4 days.
11. What is the name of the process by which sperm gain the ability to fertilize an oocyte?
A) Acrosome reaction
B) Capacitation
C) Spermiogenesis
D) Fertilization
Answer: B – Capacitation.
200 Practice Questions and Verified Answers | Complete Q&A
Guide | A+ Graded
SECTION 1: GAMETOGENESIS AND FERTILIZATION (Questions 1–35)
1. A male patient presents with azoospermia due to a mutation in the gene encoding the catalytic
subunit of protein kinase A (PKA). Which step of spermatogenesis is most likely directly impaired?
A) Mitotic proliferation of spermatogonia
B) Meiotic recombination in primary spermatocytes
C) Acrosome formation during spermiogenesis
D) Flagellar assembly in spermatids
Answer: C – Acrosome formation during spermiogenesis.
Rationale: PKA signaling is crucial for acrosome biogenesis during spermiogenesis. Mitotic proliferation
and meiotic recombination rely on different kinases (e.g., CDKs). Flagellar assembly involves
intraflagellar transport proteins, not PKA directly.
2. In a mouse model, deletion of the gene encoding ZP3 results in female infertility. Which step of
fertilization is primarily disrupted?
A) Sperm capacitation in the female tract
B) Acrosome reaction upon zona binding
C) Spermzona pellucida binding
D) Fusion of sperm and oolemma
Answer: C – Spermzona pellucida binding.
Rationale: ZP3 is the primary sperm receptor in the zona pellucida; its absence prevents initial binding.
Capacitation occurs before zona binding, and fusion requires different proteins.
,3. 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) Spermegg fusion
Answer: C – Block to polyspermy after cortical granule exocytosis.
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.
4. During oogenesis, the primary oocyte is arrested at the 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 anaphasepromoting complex (APC)
D) Low cAMP levels in the oocyte
Answer: B – Phosphorylation and inactivation of MPF by Wee1 kinase.
Rationale: Meiotic arrest is maintained by Wee1 kinasemediated phosphorylation of CDK1, keeping MPF
inactive. High cAMP also contributes but is not the primary mechanism.
5. Which of the following is the correct sequence of developmental stages in the pig embryo?
A) Zygote, 2cell, 4cell, 8cell, 16cell, morula, blastocyst, expanded blastocyst, hatched blastocyst
B) Zygote, morula, blastocyst, 2cell, 4cell, 8cell, 16cell
C) Morula, zygote, 2cell, 4cell, 8cell, 16cell, blastocyst
D) 2cell, 4cell, 8cell, zygote, 16cell, morula, blastocyst
Answer: A – Zygote, 2cell, 4cell, 8cell, 16cell, morula, blastocyst, expanded blastocyst, hatched
blastocyst.
,Rationale: This is the correct sequence of embryonic development following fertilization.
6. Which of the following is NOT a germ layer of the embryo?
A) Ectoderm
B) Mesoderm
C) Endoderm
D) Trophoblast
Answer: D – Trophoblast.
Rationale: The three germ layers are ectoderm, mesoderm, and endoderm. The trophoblast is an
extraembryonic tissue that contributes to the placenta.
7. What portion of the blastocyst actually becomes the developing embryo?
A) Trophoblast
B) Inner cell mass
C) Blastocoel
D) Zona pellucida
Answer: B – Inner cell mass.
Rationale: The inner cell mass gives rise to the embryo proper. The trophoblast forms the placenta.
8. Which of the following statements about female and male gametogenesis is incorrect?
A) Male meiosis is completed in days or weeks
B) Female meiosis is delayed for months or years
C) The total number of oocytes is regulated by follicle stimulating hormone
D) Spermatogenesis produces four functional gametes from each primary spermatocyte
Answer: C – The total number of oocytes is regulated by follicle stimulating hormone.
, Rationale: The total number of oocytes is determined before birth and is not regulated by FSH. FSH
stimulates follicular development but does not increase the total oocyte count.
9. Normal fertilization typically occurs in which location?
A) Ovary
B) Uterus
C) Ampulla of the fallopian tube
D) Vagina
Answer: C – Ampulla of the fallopian tube.
Rationale: Fertilization usually occurs in the ampulla (the widest portion) of the fallopian tube.
10. Upon entering the vagina, spermatozoa have up to how many days to fertilize the oocyte?
A) 1 day
B) 2 days
C) 4 days
D) 7 days
Answer: C – 4 days.
Rationale: Spermatozoa can survive in the female reproductive tract for up to 4 days.
11. What is the name of the process by which sperm gain the ability to fertilize an oocyte?
A) Acrosome reaction
B) Capacitation
C) Spermiogenesis
D) Fertilization
Answer: B – Capacitation.
