The fertilisation cone, which pulls the sperm into the egg, is formed from
A) Acrosome of the sperm
B) Aero somal process of the sperm
C) Vitelline layer of the egg
D) Plasma membrane of the egg

Hint:The union of male sperm and female egg to form a zygote is known as fertilisation. A cone like projection protruding from the surface of eggs at the point of contact with the sperm is called fertilisation cone.

Complete Answer:
The human sperm is a highly mobile structure which consist of
Acrosomal head- It is the covering around the head which contains enzymes called acrosome which helps in penetration of sperm into the egg.
Body- It contains nucleus, mitochondria and other organelles.
Flagella- It helps in movement. The tail is activated by the process called capacitation when it enters the female body.
Once the sperm reaches the egg, the enzyme in the acrosome is activated. This is called an acrosome reaction. During this process the fertilisation cone is developed on the surface of the plasma membrane of the egg which pulls the sperm towards itself. It enables the sperm to penetrate the thick coat surrounding the egg.
The membrane of sperm fuses with egg and sperm nucleus fuses with the egg.


Vitelline layer of egg- It is a transparent layer which encloses the yolk of hen’s egg.
The correct answer is the fertilisation cone, which pulls the sperm into the egg, is formed from the plasma membrane.


Hence the correct answer is option ‘D’.

Note:The acrosome reaction allows the sperm to penetrate the zona pellucida of the egg. It stimulates the fusion between the plasma membrane and the acrosomal membrane by forming a cone like structure which helps in easy penetration of sperm in the egg.