During fertilization, the point of entry of sperm is

Rotation centre of embryo

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Axis of cleavage

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Grey crescent

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Dorsal lip of blastopore

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Solution

The correct option is A Rotation centre of embryo
The entry point of the sperm during fertilization in the animal hemisphere will determine the future dorsal-ventral axis of the zygote. The sperm centrosome initiates formation of the sperm aster and cortical rotation follows via a microtubule-dependent process. The rotation of a fertilized frog egg results in the formation of the grey crescent, which will become the Nieuwkoop center. Cortical rotation is necessary for establishing the dorsal-ventral axis of the egg, in the absence of rotation no dorsal structures form (muscles, nervous system, etc.) and in the case of over rotation no ventral structures form (gut, endoderm, etc.).
Therefore, the correct answer is option A.

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Question 47
In the given figure below, label the parts and mention their functions.
1. Production of egg
2. Site of fertilization
3. Site of implantation
4. Entry of the sperms

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