Q20. Which sperm part contains the X or Y chromosome involved in determining chromosomal sex?
[RRB Group D — 30 September 2022]
(A) Middle piece
(B) Head
(C) Tail
(D) Neck only
Answer: (B) Head
Explanation: The sperm head contains the haploid nucleus bearing either an X or a Y chromosome. The oocyte ordinarily provides an X chromosome. Combining these at fertilisation establishes the typical XX or XY chromosomal complement of the resulting zygote.
Q19. Which embryological process produces the three primary germ layers?
[DSSSB PGT Biology (Female) — 16 July 2021]
(A) Fertilisation
(B) Cleavage
(C) Gastrulation
(D) Spermiogenesis
Answer: (C) Gastrulation
Explanation: Gastrulation reorganises early embryonic cells into ectoderm, mesoderm and endoderm. These layers give rise to different tissues and organ systems during later differentiation. Fertilisation forms the zygote, cleavage increases blastomere number, and spermiogenesis produces mature sperm morphology.
Q18. When does a human secondary oocyte complete its second meiotic division?
[NEET UG — 2020]
(A) Before entering the fallopian tube
(B) After the entry of a sperm
(C) During fetal ovarian development
(D) Only after implantation
Answer: (B) After the entry of a sperm
Explanation: The secondary oocyte remains arrested in metaphase II after ovulation. Sperm entry triggers completion of meiosis II, generating the mature ovum and second polar body. This is followed by formation and fusion of pronuclei to establish the zygote.
Q17. Which description correctly explains the expression “test-tube baby”?
[RRB Junior Engineer — 31 May 2019]
(A) Both fertilisation and development occur in a tube
(B) Fertilisation occurs outside the body and further development occurs in the uterus
(C) Fertilisation occurs only in the uterus but birth is in a laboratory
(D) The embryo develops entirely outside the maternal body
Answer: (B) Fertilisation occurs outside the body and further development occurs in the uterus
Explanation: The popular expression refers to in vitro fertilisation followed by embryo transfer. Gametes are brought together under controlled laboratory conditions; after initial development, an embryo is placed in the uterus, where implantation and subsequent fetal development can occur.
Q16. Fertilisation in humans is normally classified as which type?
[SSC MTS — 14 August 2019]
(A) Internal fertilisation
(B) External fertilisation
(C) External budding
(D) Vegetative fertilisation
Answer: (A) Internal fertilisation
Explanation: In humans, sperm and secondary oocyte ordinarily unite within the female reproductive tract, specifically the oviduct. This is internal fertilisation. External fertilisation takes place outside the body, such as in many aquatic animals, and is not the normal human mechanism.
Q15. Which is the correct route followed by sperm from the seminiferous tubules?
[NEET UG — 2019]
(A) Seminiferous tubules → epididymis → rete testis → vas deferens
(B) Seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens
(C) Seminiferous tubules → vas deferens → rete testis → epididymis
(D) Seminiferous tubules → ureter → bladder → urethra
Answer: (B) Seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens
Explanation: Sperm leave seminiferous tubules through the rete testis, then pass into the vasa efferentia and epididymis. Following maturation and storage, they travel along the vas deferens toward the ejaculatory duct. The ureter belongs to the urinary system.
Q14. Which early milk contains important maternal antibodies for the newborn?
[UPSC CDS — 18 November 2018]
(A) Ordinary milk secreted months after birth
(B) Transitional milk alone
(C) Colostrum
(D) Artificially fortified water
Answer: (C) Colostrum
Explanation: Colostrum is the yellowish first milk produced immediately after childbirth. It contains high concentrations of protective antibodies and useful proteins. Its immunological benefits are particularly valuable before the infant’s own immune defences become fully mature, making early feeding important.
Q13. Arrange these reproductive events in order:
1. Implantation;
2. Ovulation;
3. Sex determination;
4. Fertilisation.
[UPPSC LT Grade Assistant Teacher (Home Science) — 29 July 2018]
(A) 4, 3, 1, 2
(B) 2, 4, 3, 1
(C) 2, 3, 1, 4
(D) 1, 3, 4, 2
Answer: (B) 2, 4, 3, 1
Explanation: Ovulation releases the secondary oocyte; fertilisation follows if sperm reaches it. Chromosomal sex is fixed at fertilisation by the sperm’s X or Y chromosome, so these events are essentially simultaneous biologically. Cleavage precedes later implantation of the blastocyst.
Q12. The release of mature spermatozoa from Sertoli cells into seminiferous tubule lumens is called what?
[UPPSC GIC Lecturer (Zoology) — 2017]
(A) Spermiation
(B) Azoospermia
(C) Spermiogenesis
(D) Oogenesis
Answer: (A) Spermiation
Explanation: Spermiation is the detachment and release of differentiated spermatozoa from Sertoli cells into the seminiferous tubule lumen. Spermiogenesis is the preceding transformation of spermatids into spermatozoa. Azoospermia is the absence of sperm in ejaculated semen.
Q11. Where does sperm formation occur inside the testes?
[RPSC Second Grade Teacher (Science) — 1 July 2017]
(A) Epididymis
(B) Vas deferens
(C) Prostate gland
(D) Seminiferous tubules
Answer: (D) Seminiferous tubules
Explanation: Spermatogenesis takes place in the germinal epithelium of seminiferous tubules, supported by Sertoli cells. The epididymis is important for later sperm maturation and storage. The vas deferens transports sperm, while the prostate adds secretions to semen.
