Pre-Fertilisation Events - Gametogenesis - UNSOLVED PRACTICE SET
Chapter: Reproduction in Organisms | Topic: Pre Fertilisation Events Gametogenesis
PRE-FERTILISATION EVENTS - GAMETOGENESIS - UNSOLVED PRACTICE SET
Topic: Pre Fertilisation Events Gametogenesis
Multiple Choice Questions
Q1. Gametogenesis refers to the process of:
- Fusion of gametes
- Formation of male and female gametes through meiotic division
- Development of the embryo
- Formation of the zygote
Q2. In humans, spermatogenesis occurs in the:
- Ovary
- Seminiferous tubules of the testes
- Epididymis
- Prostate gland
Q3. The reduction of chromosome number from diploid (2n) to haploid (n) during gametogenesis is essential because:
- It makes the gametes smaller
- It ensures that the chromosome number is restored to 2n after fertilisation
- It increases the size of the gametes
- It prevents the gametes from moving
Q4. During oogenesis in humans, the first meiotic division is completed:
- Before birth
- At puberty, one primary oocyte per menstrual cycle completes meiosis I
- Immediately after fertilisation
- During embryonic development only
Q5. The structure formed after the first meiotic division in oogenesis is:
- A single large ovum and a polar body
- Two equal-sized ovum cells
- Four equal-sized ovum cells
- A zygote
Short Answer Questions
Q6. Define gametogenesis. Differentiate between spermatogenesis and oogenesis in terms of: site of occurrence, number of gametes produced from one germ cell, and whether the divisions are equal or unequal.
Q7. Why is meiosis essential during gametogenesis? What would happen if gametes were formed by mitosis instead of meiosis?
Q8. Explain why oogenesis produces one functional ovum and polar bodies, while spermatogenesis produces four functional sperm. What is the biological significance of this difference?
Q9. A human cell has 46 chromosomes. How many chromosomes would be present in: (a) a primary spermatocyte, (b) a secondary spermatocyte, (c) a spermatid, and (d) a sperm? Show the progression.
Long Answer Questions
Q10. Explain gametogenesis in detail. Describe spermatogenesis (spermatogonia → primary spermatocyte → secondary spermatocyte → spermatid → sperm) and oogenesis (oogonia → primary oocyte → secondary oocyte → ovum), highlighting the role of meiosis, the differences in timing between male and female gamete formation, and the significance of reduction division in maintaining chromosome number across generations.
Q11. "Oogenesis is a story of conservation and sacrifice, while spermatogenesis is a story of mass production." Analyse this statement by comparing: the number of gametes produced, the energy investment per gamete, the unequal cytokinesis in oogenesis versus equal cytokinesis in spermatogenesis, and the evolutionary reasons behind these differences in reproductive strategies.
APPLICATION / ANALYSIS
Q12. Case Study — Gamete Formation Disorders:
A genetic counselling centre received three cases:
| Case | Condition | Effect on Gametogenesis |
|---|---|---|
| Patient A | Klinefelter syndrome (XXY) | Reduced or absent sperm production |
| Patient B | Turner syndrome (XO) | Ovarian dysgenesis, no functional ova |
| Patient C | Chemotherapy treatment | Destroys dividing germ cells |
Answer the following:
(a) Why does an extra X chromosome in Patient A (XXY) disrupt spermatogenesis? Explain the role of the Y chromosome in male gamete formation.
(b) Patient C, a 25-year-old woman about to undergo chemotherapy, is advised to freeze her eggs. Why is this recommended before treatment rather than after? Explain based on the process of oogenesis.
(c) A researcher is trying to create artificial gametes from skin cells. What fundamental cellular process would need to be reversed or simulated to convert a diploid skin cell into a haploid gamete?
Q13. Real-Life Application - Fertility Clinic Data:
A fertility clinic in Mumbai analysed sperm samples from 100 men:
| Parameter | Normal range | Men outside normal range |
|---|---|---|
| Sperm count | >15 million/ml | 30 men had <5 million/ml |
| Sperm motility | >40% motile | 25 men had <20% motile |
| Sperm morphology | >4% normal shape | 20 men had <2% normal |
Answer the following:
(a) If a man has a sperm count of 2 million/ml, calculate how many sperm would be in a 3 ml ejaculate. Compare this to the expected number in a normal sample of the same volume.
(b) Why is sperm motility crucial for fertilisation, especially in internal fertilisation? What structure in the sperm provides the energy for movement?
(c) The clinic recommends lifestyle changes (quit smoking, reduce alcohol, exercise) to improve sperm quality. How might these factors affect the process of spermatogenesis?