COMPETITIVE EXAM MCQs SERIES of LIFE SCIENCES for CSIR-UGC NET/JRF, SLET, GATE, and other entrance tests: DEVELOPMENTAL BIOLOGY – Biology of Gametogenesis and Fertilisation.
Syllabus Outline
- Production of gametes.
- Cell surface molecules in sperm-egg recognition in animals.
- Embryo sac development and double fertilisation in plants.
This quiz contains 25 concept-based, most frequently asked MCQs on “DEVELOPMENTAL BIOLOGY – Biology of Gametogenesis and Fertilisation”. Each question has a single correct/most appropriate answer.
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1. A researcher treats mammalian cumulus-oocyte complexes with a PDE3A inhibitor in vitro. What is the expected effect on oocyte maturation?
A) Accelerated germinal vesicle breakdown and polar body extrusion.
B) Prevention of meiotic resumption even after removal of cGMP.
C) Induction of Metaphase II arrest without completing Meiosis I.
D) Degradation of cyclin B and immediate entry into interphase.
2. Which of the following factors is primarily responsible for maintaining high cGMP levels in the follicular environment of a mammalian ovary?
A) EGF acting on the EGF receptor in granulosa cells.
B) C-type natriuretic peptide acting on NPR2 in granulosa and cumulus cells.
C) Progesterone acting on intracellular receptors in cumulus cells.
D) Follicle-stimulating hormone acting on theca cells.
3. A mutation in Emi2 prevents it from binding to the Anaphase-Promoting Complex. What would be the most likely consequence during oocyte maturation?
A) Permanent arrest at Prophase I.
B) Spontaneous parthenogenetic activation.
C) Inability to complete the first meiotic division.
D) Formation of a triploid zygote upon fertilisation.
4. In sea urchin fertilisation, the sperm protein bindin mediates species-specific binding to the egg’s vitelline envelope. Where is bindin located before the acrosome reaction?
A) On the outer surface of the sperm plasma membrane.
B) Sequestered within the acrosomal vesicle.
C) Within the mitochondria of the sperm midpiece.
D) Associated with the sperm flagellar microtubules.
5. In frogs, the fast block to polyspermy is mediated by depolarisation of the egg membrane. Which channel and ion flow are responsible for this depolarisation?
A) Voltage-gated Na⁺ channel; influx of Na⁺ from pond water.
B) A Na⁺-permeable channel; altered Na⁺ flux.
C) NMDA receptor; influx of Ca²⁺.
D) Aquaporin; efflux of water and ions.
6. In sea urchins, the cortical granule reaction leads to the formation of the fertilisation envelope. Which enzyme cross-links tyrosine residues to harden this envelope?
A) Transglutaminase
B) Furin
C) Calreticulin
D) Ovoperoxidase
7. The acrosome reaction in sea urchin sperm is specifically triggered by:
A) The decrease in pH as sperm enters the female reproductive tract.
B) The release of progesterone from the egg.
C) The binding of bindin to the EBR1 receptor.
D) Sulfated polysaccharides found in the egg jelly coat.
8. During the slow block to polyspermy in sea urchins, Ca²⁺ ions are released from the endoplasmic reticulum. Which signalling molecule initiates this Ca²⁺ release?
A) Diacylglycerol
B) Sphingosine-1-phosphate
C) Cyclic AMP
D) Inositol trisphosphate
9. A researcher creates a chimeric sea urchin bindin protein in which the species-specific binding domain is replaced with the equivalent domain from a different sea urchin species. What would most likely happen when sperm carrying this chimeric bindin are used in a fertilisation assay?
A) The sperm would be unable to undergo the acrosome reaction.
B) The sperm would be attracted chemotactically toward the wrong species’ egg jelly.
C) The sperm would bind specifically to eggs of the donor species whose domain was used.
D) The sperm would be unable to swim due to defective dynein-ATPase activity.
10. The fast block to polyspermy in sea urchins is mediated by Na⁺ influx, causing membrane depolarisation. If sea urchin eggs are fertilised in a medium with very low Na⁺ concentration, what would be the expected outcome?
A) Fertilisation is blocked.
B) The rate of polyspermy increases.
C) The eggs fail to undergo the cortical granule reaction.
D) The sperm cannot undergo the acrosome reaction.
11. In the development of a monosporic, 8-nucleate Polygonum-type embryo sac, how many rounds of meiosis and mitosis occur, starting from the megaspore mother cell?
A) 1 round of meiosis, 1 round of mitosis.
B) 1 round of meiosis, 2 rounds of mitosis.
C) 1 round of meiosis, 3 rounds of mitosis.
D) 2 rounds of meiosis, 3 rounds of mitosis.
12. The “Bambacioni Effect” is a defining feature of the Fritillaria-type embryo sac. What occurs during this process?
A) All four megaspores degenerate, and the embryo sac develops from nucellar cells.
B) The egg cell and synergids fuse to form a triploid zygote.
C) The central cell undergoes an extra mitosis to produce four polar nuclei.
D) Three of the four haploid megaspore nuclei fuse to form a triploid (3n) nucleus at the chalazal end.
13. In a feronia mutant of Arabidopsis, what characteristic phenotype is observed during pollen tube reception?
A) The pollen tube cannot find the micropyle and grows randomly within the ovary.
B) The pollen tube enters the synergid but fails to cause membrane rupture.
C) The pollen tube ruptures prematurely in the style before reaching the ovule.
D) Synergid cells fail to differentiate and do not form a filiform apparatus.
14. Which cell in a mature Polygonum-type embryo sac is triploid (3n) following double fertilisation?
A) Zygote
B) Synergid
C) Primary Endosperm Nucleus
D) Antipodal cell
15. The Allium-type embryo sac is classified as bisporic. What does this mean?
A) It develops from two separate megaspore mother cells.
B) It develops from one of the two dyad cells formed after the first meiotic division.
C) It contains two egg cells, both of which are fertilised.
D) It involves two meiotic divisions followed by only one mitotic division.
16. In the Oenothera-type embryo sac, which structure is typically absent?
A) Egg apparatus
B) Polar nuclei
C) Antipodal cells
D) Central cell
17. What does double fertilisation ensure in angiosperms?
A) Two embryos are formed in each seed to increase survival chances.
B) Endosperm develops only when egg fertilisation occurs.
C) The zygote is always triploid to allow for a larger seed size.
D) The pollen tube can fertilise two different ovules simultaneously.
18. In a tetrasporic embryo sac of the Adoxa type, the mature gametophyte nuclei are derived from:
A) A single mitotic division of each of the four megaspore nuclei.
B) Three mitotic divisions of a single chalazal megaspore.
C) Two mitotic divisions of a functional dyad cell.
D) Fusion of nucellar cells with the megaspore nucleus.
19. In the Fritillaria-type embryo sac, what is the ploidy of the primary endosperm nucleus formed after double fertilisation?
A) 3n
B) 4n
C) 5n
D) 6n
20. In plants, once fertilisation is complete, what mechanism is thought to prevent additional pollen tubes from entering the same ovule?
A) Rapid depolarisation of the synergid membrane.
B) Degeneration of the remaining synergid and cessation of attractant.
C) Hardening of the nucellus into a thick, impenetrable wall.
D) Cleavage of the attractant by ovastacin released from the central cell.
21. The “Zinc Spark” is a phenomenon observed during mammalian and amphibian fertilisation. What is its physiological significance?
I – It inhibits sperm surface enzymes
II – It modifies the egg’s extracellular matrix to prevent polyspermy.
III – It acts as a chemoattractant for additional sperm as a backup mechanism.
IV – It triggers immediate Zn²⁺ influx responsible for the fast block.
A) I only
B) I and II
C) I, II and III
D) I, II, III and IV
22. Which of the following statements about bindin is correct?
I – It is a species-specific adhesive protein.
II – It possesses fusogenic properties that help sperm and egg membranes fuse.
III – Its exposure on the sperm surface requires the acrosome reaction.
IV – It is a glycoprotein receptor located on the egg’s vitelline membrane.
A) I Only
B) I and II
C) I, II and III
D) I, II, III and IV
23. Assertion (A): The fast block to polyspermy is absent in most mammalian species.
Reason (R): In mammals, internal fertilisation results in very few sperm reaching the egg, making a fast electrical block less necessary compared to external fertilisers.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is NOT the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.
24. Assertion (A): Closure of gap junctions between cumulus cells and the oocyte is necessary for meiotic resumption.
Reason (R): Gap junctions transport cGMP and cAMP from granulosa cells into the oocyte, keeping CDK1 in an active state.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is NOT the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.
25. Assertion (A): Synergid cells are essential for successful double fertilisation.
Reason (R): Synergids secrete chemoattractant peptides and provide the site for pollen tube reception and sperm cell release.
A) Both A and R are true, and R is the correct explanation of A.
B) Both A and R are true, but R is NOT the correct explanation of A.
C) A is true, but R is false.
D) A is false, but R is true.
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References
- Michael Barresi and Scott Gilbert (2023). Developmental Biology, Oxford University Press, 13th Edition.
- Lincoln Taiz, Ian Max Møller, Angus Murphy, and Eduardo Zeiger (2022). Plant Physiology and Development, Oxford University Press, 7th Edition.
- Geoffrey Cooper and Kenneth Adams (2022). The Cell: A Molecular Approach, Oxford University Press, 9th Edition.
- Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K., & Walter, P. (2014). Molecular Biology of the Cell, Garland Science, 4th Edition.
- Robert A Weinberg, Robert A. Weinberg (2006). The Biology of Cancer, Taylor & Francis, 1st Edition.
- Gupta, P.K. (2022). Cell and Molecular Biology, Rastogi Publications, 5th Edition.
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