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Multiple Choice
Which of the following processes occurs after oocyte activation and the completion of meiosis II?
A
Fusion of the male and female pronuclei
B
Initiation of DNA replication in the secondary oocyte
C
Formation of the synaptonemal complex
D
Release of the first polar body
Verified step by step guidance
1
Understand the context: Oocyte activation occurs after fertilization, which is the fusion of a sperm cell with an oocyte. This triggers a series of events leading to the completion of meiosis II in the oocyte.
Recall the key events after oocyte activation: After meiosis II is completed, the oocyte forms a mature ovum and releases the second polar body. The male and female pronuclei then fuse to form a single diploid nucleus, which is essential for the zygote's development.
Eliminate incorrect options: Formation of the synaptonemal complex is a process that occurs during meiosis I, not after oocyte activation. Release of the first polar body happens during meiosis I, not meiosis II. Initiation of DNA replication in the secondary oocyte is not relevant to this stage of development.
Focus on the correct process: Fusion of the male and female pronuclei is the key event that occurs after oocyte activation and the completion of meiosis II. This fusion combines the genetic material from both parents into a single nucleus.
Summarize the reasoning: The correct answer is 'Fusion of the male and female pronuclei' because it is the critical step that follows oocyte activation and meiosis II, leading to the formation of a zygote.