Question

1. What is monospermy? What is its purpose?

2. The secondary oocyte has how many chromosomes?

3. What is the corona radiata?

4. What is the zona pellucida?

5. What is a pronulecus?

Answer 1

Answer

1) Monospermy is fetilization of the ovum by only one sperm.

• When one sperm fertilize the egg, it forms amembrane surrounding the ovum that prevents entry of other sperms (prevents polyspermy).
• Polyspermy is prevented as it might alter partitioning of chromosomes.

2) The secondary oocyte is haploid and contains 23 chromosomes.

3) Corona radiata is innermost layer of mature (Graffian) follicle. During ovulation, Secondary oocyte is released along with corona radiata hence, it also outer layer of the secondary oocyte made up of granulosa cells.
- It functions to supply essential proteins to the oocyte.

4) Zona pellucida is innermost layer that is in direct contact with plasma membrane of seconday oocyte. It is made up of glycoproteins.
- Sperm must penetrate zona pellucida in order to bind to the plasma membrane of the oocyte.
- This helps to prevent attachment of oocyte while travel down the uterine tube.

5) Pronucleus is the nucleus of male or female gamete just prior to their fusion.
Fusion of haploid pronucleus forms a zygote after fertilization.