6. 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

---

What is Capacitation?

Capacitation refers to a series of biochemical and physiological changes that mammalian spermatozoa undergo after entering the female reproductive tract, especially within the oviduct (fallopian tubes). This process is necessary for sperm to acquire fertilization competence—making them capable of penetrating and fertilizing the egg.

---

The Biological Process of Capacitation

After ejaculation, sperm in the male reproductive tract are not yet ready to fertilize the egg. Upon entering the female tract, sperm interact with the secretions and environment inside the oviduct, which triggers capacitation. Key changes during capacitation include:

• Removal of cholesterol and other stabilizing molecules from the sperm membrane, increasing membrane fluidity.

• Increased permeability to calcium ions, which is vital for triggering hyperactive motility and the acrosome reaction.

• Activation of signaling pathways involving cyclic AMP (cAMP) and protein phosphorylation.

• Changes in sperm motility patterns, especially the shift to vigorous, asymmetrical tail movements known as hyperactivation.

These changes collectively enable the sperm to undergo the acrosome reaction, where enzymes are released to help the sperm penetrate the protective layers surrounding the egg.

---

Importance of Capacitation

Capacitation is essential for fertilization because:

• It primes sperm to bind and fuse with the egg membrane.

• Without capacitation, sperm remain motile but are unable to fertilize the egg.

• It ensures sperm become biochemically and physiologically competent only at the right time and place, avoiding premature acrosome reaction.

---

Why Other Statements Are Incorrect

• Meiotic division in the egg after sperm penetration (Option 2): This refers to the resumption of the second meiotic division in the egg triggered by fertilization, not sperm capacitation.

• Maturation of egg in oviduct after fertilization (Option 3): Eggs mature before fertilization during ovulation; capacitation is unrelated to egg maturation.

• Release of egg after maturation (Option 4): This is ovulation, the process of egg release, separate from sperm capacitation.

---

Conclusion

The correct definition of capacitation is the maturation process undergone by mammalian spermatozoa after entering the female oviduct to gain fertilization competence. This process is indispensable for successful fertilization in mammals.

Therefore, the correct answer is:

(1) is the maturation of mammalian spermatozoa after entering into oviduct of female.