Question

Which of the following is responsible for the formation of fertilisation cone?

• A. Plasma membrane of the sperm cell.
• B. Plasma membrane of the oocyte
• C. Zona pellucida
• D. Corona radiata

Answer 1

The correct option is B Plasma membrane of the oocyte

After the sperm has penetrated through various layers of the oocyte (corona radiata, zona pellucida), the plasma membrane makes a slight rise in the upward direction to form a structure called the reception cone or the fertilisation cone which receives the incoming sperm.

Though the fusion of the plasma membranes of both gametes initiates the formation of fertilisation cone, it is the plasma membrane of the oocyte that forms the cone and not the sperm cell.

The zona pellucida and corona radiata layers of the oocyte are not involved in the formation of fertilisation cone.

AS the sperm approaches, a portion of the corona radiata and the zona pellucida layer is degraded to allow the entry of the sperm. The entire layer is not digested.

In the subsequent stages, the zona pellucida layer hardens due to cortical enzymes secretion. This hardening is essential for blocking additional sperms to enter the oocyte.