Test: Fertilisation - NEET MCQ

The ovum released by the ovary is also transported to the ampullary region where fertilisation takes place. Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary region.

Line in NCERT: "The infundibulum leads to a wider part of the oviduct called ampulla."

During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum  and induces changes in the membrane that block the entry of additional sperms. Thus, it ensures that only one sperm can fertilise an ovum.

Line in NCERT: "During fertilisation, a sperm comes in contact with the zona pellucida layer of the ovum and induces changes in the membrane that block the entry of additional sperms."

The haploid ovum is formed after the second round of meiosis is completed. This haploid ovum is also called ootid. Oogonium is the egg mother cell that is diploid and undergoes meiosis to form an egg.

Acrosome of Sperm have enzymes for Sperm wall digestion.

Line in NCERT: "The acrosome is filled with enzymes that help fertilisation of the ovum."

Sperms are released into the vagina. From here, they travel through the cervix and uterus before reaching the  oviduct or fallopian tube, where they can encounter an egg.

Line in NCERT: "Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary region."

The correct order of layers or spaces from outside to inside is:

1. Zona pellucida: The glycoprotein layer surrounding the oocyte.
2. Perivitelline space: The space between the zona pellucida and the plasma membrane of the oocyte.
3. Plasma membrane: The membrane that encloses the oocyte cytoplasm.

Thus, the order is Zona pellucida → Perivitelline space → Plasma membrane.

• The secondary oocyte released from the ovary has finished first round of meiosis.
• The second round of meiosis occurs in ampulla after the egg encounters the sperm.
• This leads to formation of large ovum and a tiny second polar body.

The fusion of sperm and egg restores the chromosome number.

The new cell is called zygote having the potential to develop into a new organism.

Line in NCERT: "Soon the haploid nucleus of the sperms and that of the ovum fuse together to form a diploid zygote."

• Sperm and egg are haploid cells hence have only one set of chromosomes.
• Zygote on the other hand is diploid thus has 46 chromosomes.

Line in NCERT: "The zygote would carry either XX or XY depending on whether the sperm carrying X or Y fertilised the ovum."

Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary-isthmic junction and ovum is released only once a month. This is the reason why all copulations do not lead to fertilisation and pregnancy.

Line in NCERT: "Fertilisation can only occur if the ovum and sperms are transported simultaneously to the ampullary region. This is the reason why not all copulations lead to fertilisation and pregnancy."