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Question
Which of the following statements is true about fertilisation?
Which of the following statements is true about fertilisation?
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Solution
The correct option is B The entry of sperm into the ooplasm stimulates the oocyte for completing meiosis.
The entry of the sperm into the ooplasm (cytoplasm of the oocyte) is essential for the oocyte to complete its meiosis II of cell division.
Oogonia are female gamete mother cells that undergo meiosis and get arrested at prophase I at birth. At this stage they are called primary oocytes.
At puberty, the primary oocyte completes its meiosis I and commences meiosis II. After completion of meiosis I, it forms a secondary oocyte and first polar body. Then it gets arrested at metaphase of meiosis II and does not advance further until fertilisation.
After the entry of the sperm into the oocyte, the oocyte completes its second meiotic division.
It is not true that only one sperm reaches the egg. Infact many sperms reach the egg, but only one is able to penetrate it. The rest of the sperms are prevented from entering the oocyte by block to polyspermy.
During amphimixis, the 2 haploid pronuclei (male and female pronuclei) are formed after fusion of gametes. These fuse to produce a single diploid nucleus. It doesn’t undergo any meiotic division, hence it doesn’t become haploid.
In case of sperm entry into the egg, not only the acrosome, but the entire sperm enters the egg. After the formation of the pronucleus from the sperm nucleus, the rest of the sperm cell degenerates.
The entry of the sperm into the ooplasm (cytoplasm of the oocyte) is essential for the oocyte to complete its meiosis II of cell division.
Oogonia are female gamete mother cells that undergo meiosis and get arrested at prophase I at birth. At this stage they are called primary oocytes.
At puberty, the primary oocyte completes its meiosis I and commences meiosis II. After completion of meiosis I, it forms a secondary oocyte and first polar body. Then it gets arrested at metaphase of meiosis II and does not advance further until fertilisation.
After the entry of the sperm into the oocyte, the oocyte completes its second meiotic division.
It is not true that only one sperm reaches the egg. Infact many sperms reach the egg, but only one is able to penetrate it. The rest of the sperms are prevented from entering the oocyte by block to polyspermy.
During amphimixis, the 2 haploid pronuclei (male and female pronuclei) are formed after fusion of gametes. These fuse to produce a single diploid nucleus. It doesn’t undergo any meiotic division, hence it doesn’t become haploid.
In case of sperm entry into the egg, not only the acrosome, but the entire sperm enters the egg. After the formation of the pronucleus from the sperm nucleus, the rest of the sperm cell degenerates.
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