In oogenesis, which of the following events occurs immediately following the completions of meiosis II?
(A) Degeneration of the zona pellucida
(B) Sperm penetration of the corona radiata
(C) Formation of a female pronucleus
(D) Appearance of the blastocyst
(E) Completion of cleavage
Answer - C.
The secondary oocyte is arrested in metaphase of meiosis II, and it will remain in this meiotic stage until fertilization occurs. Following fertilization, the secondary oocyte completes meiosis II, forming a mature ovum and a polar body. The nucleus of the mature ovum is called the female pronucleus, which fuses with the male pronucleus to form a zygote.
(A) Degeneration of the zona pellucida
(B) Sperm penetration of the corona radiata
(C) Formation of a female pronucleus
(D) Appearance of the blastocyst
(E) Completion of cleavage
Answer - C.
The secondary oocyte is arrested in metaphase of meiosis II, and it will remain in this meiotic stage until fertilization occurs. Following fertilization, the secondary oocyte completes meiosis II, forming a mature ovum and a polar body. The nucleus of the mature ovum is called the female pronucleus, which fuses with the male pronucleus to form a zygote.
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