Category: CSIR NET Life Science Previous Year Questions and Solution on Gametogenesis and Fertilization

Category: CSIR NET Life Science Previous Year Questions and Solution on Gametogenesis and Fertilization

CSIR NET Life Science Previous Year Questions and Solutions on Gametogenesis and Fertilization

Gametogenesis and fertilization are fundamental topics in Developmental Biology, and they are frequently tested in CSIR NET Life Science exams. Understanding the cellular and molecular mechanisms behind these processes is essential for scoring well. Practicing previous year questions with solutions can greatly enhance your preparation.

This article provides a detailed guide on CSIR NET Life Science previous year questions and solutions related to gametogenesis and fertilization, along with preparation tips and resources.

What is Gametogenesis and Fertilization?

Gametogenesis is the process by which germ cells (sperm and egg) are formed. It ensures the transmission of genetic material to the next generation. Gametogenesis includes:

  • Spermatogenesis – Formation of sperm in males

  • Oogenesis – Formation of eggs in females

Fertilization is the union of male and female gametes to form a zygote, initiating embryonic development. It involves several steps:

  • Sperm capacitation

  • Acrosome reaction

  • Sperm-egg recognition and fusion

  • Activation of egg metabolism

Both processes are highly regulated by hormones, genes, and signaling pathways.

Importance of Practicing Previous Year Questions

Practicing CSIR NET previous year questions (PYQs) is one of the most effective strategies for preparation:

  1. Understanding Exam Pattern: Helps identify frequently asked questions.

  2. Highlighting Important Topics: Reveals high-yield areas in gametogenesis and fertilization.

  3. Time Management: Improves speed and accuracy for multiple-choice questions.

  4. Self-Evaluation: Helps identify strengths and weaknesses.

Sample Previous Year Questions on Gametogenesis and Fertilization

Here are some examples of CSIR NET Life Science previous year questions with solutions:

  1. Question: What is the role of Sertoli cells in spermatogenesis?
    Solution: Sertoli cells provide structural and nutritional support to developing sperm cells, secrete anti-Müllerian hormone, and form the blood-testis barrier.

  2. Question: Name the hormone that regulates oogenesis.
    Solution: Follicle-stimulating hormone (FSH) regulates oogenesis, promoting follicle growth and maturation. Luteinizing hormone (LH) triggers ovulation.

  3. Question: Explain the acrosome reaction.
    Solution: The acrosome reaction occurs when the sperm contacts the zona pellucida of the egg, releasing enzymes that help sperm penetrate the egg’s outer layers for fertilization.

  4. Question: What is capacitation of sperm?
    Solution: Capacitation is a functional maturation process of sperm in the female reproductive tract, making it capable of fertilizing the egg.

  5. Question: How does polyspermy get prevented?
    Solution: Polyspermy is prevented by:

    • Fast block: Change in egg membrane potential

    • Slow block (cortical reaction): Release of cortical granules modifying the zona pellucida

  6. Question: Mention one gene important for gametogenesis.
    Solution: DAZL (Deleted in Azoospermia-Like) gene is crucial for germ cell development and spermatogenesis.

Tips for Preparing Gametogenesis and Fertilization for CSIR NET

  1. Focus on Diagrams: Draw and label processes like spermatogenesis, oogenesis, and fertilization stages.

  2. Understand Hormonal Regulation: Study roles of FSH, LH, estrogen, and testosterone in gametogenesis.

  3. Molecular Basis: Learn key genes and signaling pathways involved in gamete formation.

  4. Practice PYQs: Solve previous year questions regularly to improve accuracy and speed.

  5. Use Mnemonics: For remembering stages, hormones, and gene functions.

Recommended Resources

  1. Developmental Biology by Scott F. Gilbert – Detailed explanation of gametogenesis and fertilization.

  2. Lippincott’s Illustrated Reviews: Developmental Biology – Good for diagrams and concise concepts.

  3. CSIR NET Life Science Previous Year Question PDFs – Practice questions with solutions.

  4. Online Video Lectures and Test Series – Helpful for visual learning and exam practice.

Conclusion

Gametogenesis and fertilization are high-priority topics in CSIR NET Life Science. Regular practice of previous year questions with solutions not only strengthens conceptual understanding but also improves problem-solving speed and exam confidence.

Tip: Dedicate daily practice time to 2–3 questions on gametogenesis and fertilization, revise diagrams weekly, and track your progress for optimal results.

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The development of sporophyte directly from gametophytic tissue without fusion of gametes is termed as (1) Apogamy (2) Apospory (3) Adventive embryony (4) Apomixis

Apogamy in Plants: Asexual Development of Sporophyte from Gametophyte Without Fertilization

Membrane-bound, Golgi-derived structures containing proteolytic enzymes in sperms of sea urchin are called (1) cortical granules (2) micromeres (3) acrosomal vesicles (4) macromeres 

Acrosomal Vesicles in Sea Urchin Sperm: Key Players in Fertilization Through Enzymatic Action

During fertilization "in mammals, sperm-egg interaction is mediated by zona pellucida (ZP) membrane proteins and their receptors present in sperm membrane. ZP3 has been identified to be the principle ZP protein whose post-translational modification is important for sperm - egg interaction. In a competitive inhibition assay the sperm is saturated with either active ZP3 or its modified forms, before studying sperm-egg- interaction. Which of the following experiments will NOT inhibit sperm-egg-interaction (1) Saturate sperm with ZP3 protein prior to use. (2) Deglycosylate the ZP3 protein and use it for saturation of sperm. (3) Phosphorylate the ZP3 protein and use it for saturation of sperm. (4) Dephosphorylate the ZP3 protein and use it for saturation of sperm. 

Effect of ZP3 Post-Translational Modifications on Sperm-Egg Interaction and Fertilization

23. Capacitation of mammalian sperms allows them to be activated within the uterus and facilitate fertilization. The following statements were made regarding events occurring during capacitation: A. removal of cholesterol from sperm head. B. Removal of non-covalently bound glycoproteins. C. Increased expression of fibronectin. D. Decreased permeability of calcium Ions.

Key Biochemical Changes During Mammalian Sperm Capacitation: Cholesterol and Glycoprotein Removal

In an experiments, sperm removed from epididymis of a male mouse was added in a dish containing appropriate media and oocyte. No fertilization was seen. However, when sperm from epididymis were directly placed in uterus of an ovulated female, she became pregnant. These observation suggest that (1) The sperm need to travel some distance to attain fertilizing ability. (2) The oocyte secrets some biochemicals or factors which help sperm to fertilize. (3) The hormones in body help sperm to attain fertilizing ability. (4) The contents of female reproductive tract interact with sperm and activate it for fertilization 

How the Female Reproductive Tract Activates Mouse Sperm for Successful Fertilization

21. Capacitation of sperms in humans (1) occurs during copulation. (2) occurs after the acrosome reaction. (3) takes place in the ampulla of the oviduct. (4) takes place in the epididymis of testis. 

Human Sperm Capacitation: The Critical Maturation Process Occurring in the Ampulla of the Oviduct

Amphibian oocytes remain for years in the diplotene stage of meiotic prophase. Resumption of meiosis is initiated by (1) gonodatropic hormone. (2) growth hormone. (3) oestrogen.                                       (4) progesterone. 

How Progesterone Initiates Meiotic Resumption in Amphibian Oocytes

19. During fertilization in amphibians, the fusion of egg and sperm plasma is preceeded by (A) release of enzymatic contents from the acrosomal vesicle through exocytosis (B) binding and interaction of the sperm to vitelline membrane (C) chemoattraction of the sperm to the egg by soluble factors secreted by egg (D) passage of sperm through extracellular envelope   Which of the following is the correct sequence? (1) (A) → (B) → (C) → (D) (2) (B) → (A) → (C) → (D) (3) (C) → (A) → (B) → (D) (4) (C) → (B) → (A) → (D)

Stepwise Process of Fertilization in Amphibians: From Sperm Chemoattraction to Sperm Entry

. Fertilization in sea urchin involves interaction of sperm Bindin with its receptor EBR1, a 350 kDa glycoprotein on the egg vitelline membrane. The plot given below shows the status of membrane potential and levels of EBR1, Na+ and K+ in an unfertilized egg.18. Fertilization in sea urchin involves interaction of sperm Bindin with its receptor EBR1, a 350 kDa glycoprotein on the egg vitelline membrane. The plot given below shows the status of membrane potential and levels of EBR1, Na+ and K+ in an unfertilized egg.

The Crucial Role of Bindin and EBR1 in Sea Urchin Fertilization: Molecular Mechanisms and Egg Membrane Dynamics

Several marine organism release their gametes into the environment, where sperm attraction and subsequent events lead to successful fertilization. With reference to sea urchins, which one of the following statements is NOT true? (1) Additiion of resact into a drop of seawater containing sperms specifically attracts sperms of A. punctulata. (2) P3 is formed initially at the site of sperm entry and releases sequestered Ca2+ (3) Ca2+ prevents docking of cortical granules of the egg to the cell membrane. (4) Inhibitors that specifically block PLC𝛾 can be circumvented by microinjecting IP3 into the egg. 

Debunking Common Misconceptions in Sea Urchin Fertilization: The Role of Ca2+, Resact, and IP3

16. Polyspermy results when two or more sperms fertilize an egg. It is usually lethal since it results in blastomeres with different numbers and types of chromosomes. Many species therefore, have two blocks to polyspermy: the fast block and the slow block. In the case of sea urchins: (A) the fast block is immediate and causes the egg membrane resting potential' to rise which does not allow the sperm to fuse with the egg and is mediated by an influx of sodium ions. (B) the fast block is immediate and causes the egg membrane resting potential to rise which does not allow the sperm to fuse with the egg and is mediated by an efflux of sodium ions. (C) the slow block or cortical granule reaction is mediated by calcium ions (D) the slow block or cortical granule reaction is mediated by potassium ions. Which of the above statements are true? (1) (A) and (C) (2) (A) and (D) (3) (B) and (C) (4) (B) and (D)

Understanding Fast and Slow Blocks to Polyspermy in Sea Urchin Fertilization

15. For successful fertilization in sea urchin, interaction between the surface of the egg and acrosomal proteins, specifically a 30.5 kDa protein called bindin, is necessary. The following factors could affect this interaction and prevent fertilization: A. Removal of egg jelly polysaccharides. B. Removal of bindin receptors on the egg vitelline membrane. C. Removal of bindin receptors from the egg jelly. D. Removal of bindin receptors from a single cluster on the vitelline membrane.

Key Factors Affecting Bindin-Egg Interaction in Sea Urchin Fertilization and Their Role in Preventing Fertilization

Following statements are made about fertilization occurring in sea urchins: A. Chemoattraction of the sperm to the egg is mediated by sperm activating peptides like bindin. B. Exocytosis of the sperm acrosomal vesicles and release of enzymes occur. C. The capacitated sperm undergoes acrosome reaction. D. The acrosome protein mediating the critical species-specific binding event is resact. E. The slow block to polyspermy is accomplished by the cortical granule reaction. Which one of the following options represents the combination of all correct statements? (1) A and B only (2) A, B and D (3) B and E only           (4) A, B and E 

Key Events in Sea Urchin Fertilization: The Roles of Bindin, Acrosomal Reaction, and Cortical Granule Response

Consider the following events which occur during fertilization of sea urchin eggs. (A) Resact/Speract are peptides released from the egg jelly and help in sperm attraction. (B) Bindin, an acrosomal protein interacts in a species specific manner, with eggs. (C) A "respiratory burst" occurs during cross-linking of the fertilization envelope, where a calcium- dependent increase in oxygen level is observed. (D) lP3, which is formed at site of sperm entry, releases sequestered calcium leading to cortical granule exocytosis. Which of the above statement(s) is NOT true? (1) Only C (2) A and C (3) Only D (4) B and D 

Common Misconceptions in Sea Urchin Fertilization: Clarifying Calcium Signaling and Respiratory Burst

12. Successful fertilization in sea urchin demands specific interaction between proteins and receptors of sperms and eggs. In view of the above, which one of the following combinations is correct? (1) Bindin in acrosomes and bindin receptors on egg vitelline membrane (2) Bindin in egg membrane and bindin receptors in acrosomes (3) Resact on egg jelly and bindin on sperm membrane (4) Proteasomes on egg membranes and complex sugars on sperm membranes

Bindin and Its Receptors: Essential Proteins for Species-Specific Sperm-Egg Interaction in Sea Urchins

In case of sea urchin, which of the following is the correct sequence of events taking place during the interaction of sperm and egg? (1) Chemo-attraction of sperm to the egg by soluble molecules secreted by the egg → exocytosis of the sperm acrosomal vesicle to release its enzymes → binding of the sperm to the extracellular matrix of the egg → passage of sperm through this extracellular matrix → fusion of egg and sperm cell membranes. (2) Chemo-attraction of sperm to the egg by soluble molecules secreted by the egg → binding of the sperm to the extracellular matrix of the egg → exocytosis of the sperm acrosomal vesicle to release its enzymes → passage of sperm through cell membranes. (3) Chemo-attraction of sperm to the egg by soluble molecules secreted by the egg → binding of the sperm to the extracellular matrix of the egg →passage of sperm through this extracellular matrix →exocytosis of the sperm acrosomal vesicle to release its enzymes →fusion of egg and sperm cell membranes. (4) Chemo-attraction of sperm to the egg by soluble molecules secreted by the egg → passage of sperm through this extracellular matrix →binding of the sperm to the extracellular matrix of the eggs→ exocytosis of the sperm acrosomal vesicle to release its enzymes →fusion of egg and sperm cell membranes. 

Step-by-Step Sequence of Events During Sea Urchin Fertilization: From Sperm Attraction to Membrane Fusion

In echinoderms sperm direction is provided by (1) Calcineuric (2) Bindin (3) Resact (4) EBRI 

How Resact Directs Sperm During Echinoderm Fertilization: The Key to Sperm Chemotaxis

Species-specific adhesion of sperm to the egg during sea urchin fertilization, involves the interaction of the sperm adhesive protein (1) Bindin (2) Avidin (3) Fertilin (4) Cortical granule

Role of Bindin Protein in Species-Specific Sperm-Egg Adhesion During Sea Urchin Fertilization

8. The major function of cortical granules in cytoplasm of egg is to (1) Early block to polyspermy (2) Late block to polyspermy (3) Allowing meiosis to complete (4) Helping in reorganization of sperm

Function of Cortical Granules in Egg Cytoplasm: The Key to Preventing Polyspermy

Understanding Capacitation and Fertilization: Identifying the Incorrect Statement About Calcium’s Role in Mammalian Egg Activation

Which statement is correct for capacitation? (1) is the maturation of mammalian spermatozoa after entering into oviduct of female. (2) Meiotic division in egg after penetration of sperm (3) Maturation of egg in oviduct after fertilization (4) Release of egg after maturation 

 Understanding Capacitation: The Maturation Process of Mammalian Sperm in the Female Reproductive Tract

The biggest disadvantage of sexual reproduction against the asexual reproduction is (1) Only half of genetic material is passed to offspring from each parent (2) Lot of energy and time is consumed in locating mate (3) It brings unnecessary variations (4) After fertilization in many cases zygote fails to develop

Biggest Disadvantage of Sexual Reproduction Compared to Asexual Reproduction

Gametogenesis and Fertilization

Fertilization Explained: How Membrane Fusion of Sperm and Egg Leads to Zygote Formation

3. Which of the following is the last to occur after the binding of a sea urchin sperm to an egg? (1) Initiation of mRNA synthesis (2) Increase in cytosolic pH (3) Increase in intracellular calcium concentration (4) Exocytosis of cortical granules

Sequence of Events After Sea Urchin Sperm Binds to Egg: What Happens Last?

Sperms are morphologically fit but are unable to actively swim (hyper activation) due to lack of (1) Spermatogenesis (2) Spermiogenesis (3) Prostrate glands (4) Capacitation 

Why Morphologically Normal Sperms Fail to Exhibit Hyperactivation: The Role of Capacitation

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