NYUCD GENERAL EMBRYOLOGY EXAM READY - VERIFIED
QUESTIONS AND ANSWERS - COMPREHENSIVE LATEST
VERSION 2026/2027
1. What is the diploid chromosome number in humans? ANSWER 46 (23
pairs)
2. What is the haploid chromosome number in humans? ANSWER 23
3. Where are primordial germ cells (PGCs) first identifiable? ANSWER In the
wall of the yolk sac during the 3rd week of development
4. What do primordial germ cells give rise to? ANSWER Gametes (sperm and
ova)
5. What is spermatogenesis? ANSWER The process of sperm cell development
from spermatogonia through meiosis and spermiogenesis
6. What is oogenesis? ANSWER The process of ovum development from
oogonia through meiosis
7. At what stage is the primary oocyte arrested until puberty? ANSWER
Prophase I of meiosis
8. When does the secondary oocyte complete meiosis II? ANSWER Only after
fertilization by a sperm
9. What is capacitation? ANSWER The process by which sperm gain the ability
to fertilize an egg after residing in the female reproductive tract
10. Where does fertilization normally occur? ANSWER In the ampulla of the
uterine tube (fallopian tube)
11. What enzyme does the sperm release to penetrate the corona radiata?
ANSWER Hyaluronidase
12. What structure does the sperm bind to on the zona pellucida? ANSWER
ZP3 (zona pellucida glycoprotein 3)
,13. What enzyme is released from the sperm acrosome to penetrate the zona
pellucida? ANSWER Acrosin
14. What is the cortical reaction? ANSWER Release of cortical granules from
the oocyte that modify the zona pellucida to prevent polyspermy
15. What is the fast block to polyspermy? ANSWER Depolarization of the
oocyte membrane
16. What is the slow block to polyspermy? ANSWER The cortical reaction
causing zona reaction (hardening of zona pellucida)
17. What is a zygote? ANSWER The diploid cell formed by the fusion of sperm
and egg pronuclei
18. When do the pronuclei fuse? ANSWER About 12 hours after sperm entry
19. What is the morula? ANSWER A solid ball of 16–32 cells formed by
cleavage divisions, resembling a mulberry
20. What is the blastocyst? ANSWER A hollow ball of cells with an inner cell
mass and outer trophoblast layer
21. What does the inner cell mass (embryoblast) become? ANSWER The
embryo proper
22. What does the trophoblast become? ANSWER The chorion and
contributes to placental formation
23. What is the blastocoele? ANSWER The fluid-filled cavity within the
blastocyst
24. When does the blastocyst hatch from the zona pellucida? ANSWER Day
5–6
25. Where does implantation normally occur? ANSWER In the
superior/posterior wall of the uterus (endometrium)
26. What hormone maintains the endometrium for implantation? ANSWER
Progesterone
27. What is the syncytiotrophoblast? ANSWER The outer multinucleated layer
of trophoblast that invades the endometrium
28. What is the cytotrophoblast? ANSWER The inner mononucleated layer of
trophoblast that maintains cell boundaries
, 29. What structure prevents maternal and fetal blood from mixing? ANSWER
The placental barrier (placental membrane)
30. What is the function of human chorionic gonadotropin (hCG)? ANSWER It
maintains the corpus luteum and progesterone production in early pregnancy
SECTION B: FIRST TWO WEEKS — BILAMINAR DISC (Questions 31–60)
31. What are the two layers of the bilaminar germ disc? ANSWER Epiblast
(dorsal) and hypoblast (ventral)
32. What cavity forms above the epiblast? ANSWER The amniotic cavity
33. What cavity forms below the hypoblast? ANSWER The yolk sac
(primary/ventral)
34. What is the prochordal plate? ANSWER A thickened region of hypoblast at
the cranial end where the mouth will form
35. What is the cloacal membrane? ANSWER A thickened region at the caudal
end where the anus will form
36. What is the primitive streak? ANSWER A groove that appears on the
dorsal surface of the epiblast at the caudal end
37. What is Hensen's node? ANSWER The cranial thickened end of the
primitive streak containing the primitive pit
38. What is the primitive pit? ANSWER The opening at Hensen's node through
which cells migrate inward
39. What is gastrulation? ANSWER The process by which the bilaminar disc
becomes trilaminar through cell migration
40. Which layer do epiblast cells form first during gastrulation? ANSWER
Definitive endoderm (by displacing hypoblast cells)
41. What layer forms between epiblast and endoderm? ANSWER Mesoderm
42. What remains of the epiblast after gastrulation? ANSWER Ectoderm
43. What is the notochordal process? ANSWER A rod of cells extending
cranially from Hensen's node that forms the notochord
QUESTIONS AND ANSWERS - COMPREHENSIVE LATEST
VERSION 2026/2027
1. What is the diploid chromosome number in humans? ANSWER 46 (23
pairs)
2. What is the haploid chromosome number in humans? ANSWER 23
3. Where are primordial germ cells (PGCs) first identifiable? ANSWER In the
wall of the yolk sac during the 3rd week of development
4. What do primordial germ cells give rise to? ANSWER Gametes (sperm and
ova)
5. What is spermatogenesis? ANSWER The process of sperm cell development
from spermatogonia through meiosis and spermiogenesis
6. What is oogenesis? ANSWER The process of ovum development from
oogonia through meiosis
7. At what stage is the primary oocyte arrested until puberty? ANSWER
Prophase I of meiosis
8. When does the secondary oocyte complete meiosis II? ANSWER Only after
fertilization by a sperm
9. What is capacitation? ANSWER The process by which sperm gain the ability
to fertilize an egg after residing in the female reproductive tract
10. Where does fertilization normally occur? ANSWER In the ampulla of the
uterine tube (fallopian tube)
11. What enzyme does the sperm release to penetrate the corona radiata?
ANSWER Hyaluronidase
12. What structure does the sperm bind to on the zona pellucida? ANSWER
ZP3 (zona pellucida glycoprotein 3)
,13. What enzyme is released from the sperm acrosome to penetrate the zona
pellucida? ANSWER Acrosin
14. What is the cortical reaction? ANSWER Release of cortical granules from
the oocyte that modify the zona pellucida to prevent polyspermy
15. What is the fast block to polyspermy? ANSWER Depolarization of the
oocyte membrane
16. What is the slow block to polyspermy? ANSWER The cortical reaction
causing zona reaction (hardening of zona pellucida)
17. What is a zygote? ANSWER The diploid cell formed by the fusion of sperm
and egg pronuclei
18. When do the pronuclei fuse? ANSWER About 12 hours after sperm entry
19. What is the morula? ANSWER A solid ball of 16–32 cells formed by
cleavage divisions, resembling a mulberry
20. What is the blastocyst? ANSWER A hollow ball of cells with an inner cell
mass and outer trophoblast layer
21. What does the inner cell mass (embryoblast) become? ANSWER The
embryo proper
22. What does the trophoblast become? ANSWER The chorion and
contributes to placental formation
23. What is the blastocoele? ANSWER The fluid-filled cavity within the
blastocyst
24. When does the blastocyst hatch from the zona pellucida? ANSWER Day
5–6
25. Where does implantation normally occur? ANSWER In the
superior/posterior wall of the uterus (endometrium)
26. What hormone maintains the endometrium for implantation? ANSWER
Progesterone
27. What is the syncytiotrophoblast? ANSWER The outer multinucleated layer
of trophoblast that invades the endometrium
28. What is the cytotrophoblast? ANSWER The inner mononucleated layer of
trophoblast that maintains cell boundaries
, 29. What structure prevents maternal and fetal blood from mixing? ANSWER
The placental barrier (placental membrane)
30. What is the function of human chorionic gonadotropin (hCG)? ANSWER It
maintains the corpus luteum and progesterone production in early pregnancy
SECTION B: FIRST TWO WEEKS — BILAMINAR DISC (Questions 31–60)
31. What are the two layers of the bilaminar germ disc? ANSWER Epiblast
(dorsal) and hypoblast (ventral)
32. What cavity forms above the epiblast? ANSWER The amniotic cavity
33. What cavity forms below the hypoblast? ANSWER The yolk sac
(primary/ventral)
34. What is the prochordal plate? ANSWER A thickened region of hypoblast at
the cranial end where the mouth will form
35. What is the cloacal membrane? ANSWER A thickened region at the caudal
end where the anus will form
36. What is the primitive streak? ANSWER A groove that appears on the
dorsal surface of the epiblast at the caudal end
37. What is Hensen's node? ANSWER The cranial thickened end of the
primitive streak containing the primitive pit
38. What is the primitive pit? ANSWER The opening at Hensen's node through
which cells migrate inward
39. What is gastrulation? ANSWER The process by which the bilaminar disc
becomes trilaminar through cell migration
40. Which layer do epiblast cells form first during gastrulation? ANSWER
Definitive endoderm (by displacing hypoblast cells)
41. What layer forms between epiblast and endoderm? ANSWER Mesoderm
42. What remains of the epiblast after gastrulation? ANSWER Ectoderm
43. What is the notochordal process? ANSWER A rod of cells extending
cranially from Hensen's node that forms the notochord
