Question

A reaction of granules content which hardens the zona pellucida and ensures a block to polyspermy is ______________.
A. Acrosomal reaction
B. Cortical reaction
C. Acrosin reaction
D. Binding reaction

Answer 1

Hint: Semen containing thousands of sperm are inseminated into the female vagina during coitus during the fertilization process. The sperm travels into the uterus and enters the fallopian tube opening. Just a few sperm will make it possible to enter the opening of the fallopian tube.

Complete answer:
Each of the given options is discussed below:
> Acrosomal Reaction: The exocytosis of the acrosome or the fusion of the acrosome membrane with the plasma membrane of the sperm is the acrosome reaction. This approach releases the acrosomal material to the outside of the sperm and on the outer plasma membrane of the sperm reveals the inner acrosomal membrane proteins. The acrosome reaction's function is to help the sperm get through the protective coat of the egg and to allow the sperm and egg plasma membranes to fuse.
> Cortical reaction: The cortical reaction is a mechanism caused by the release of cortical granules from the egg during fertilization, which avoids polyspermia, the fusion of several sperm with one egg. The zona pellucida, a structure that covers mammalian eggs, becomes impermeable upon fertilization to stop polyspermia, preventing more sperm from joining. Upon fertilization, the structural changes in the zone are driven by exocytosis of cortical granules.
> Acrosin reaction: Acrosin functions as a protease and is a digestive enzyme. Acrosin is encoded in humans by the gene ACR. As a result of the acrosome reaction, acrosin is released from the acrosome of spermatozoa. It helps to penetrate the Zona Pellucida.
> Binding reaction: During this sperm binds to receptors on zona pellucida.

So, the correct answer is option (B), Cortical reaction.

Note: When fertilization occurs, the cell begins to divide and multiply in the fallopian tube within 24 hours. This multi-celled disconnected form is called a zygote. Later, it flies to the uterus after 3-4 days, and we now call it an embryo. The embryo grows and undergoes different processes and is bound to the uterus' endometrial layer. This process of attachment is known as implantation.