Question

A sperm without an acrosome, or having a dysfunctional acrosome is capable of performing which of the following actions?

• A. Bind to the zona pellucida of the secondary oocyte
• B. Penetrating through corona radiata
• C. Production of sperm lysins
• D. Penetrating the oolemma

Answer 1

The correct option is B Penetrating through corona radiata

The acrosome is present in the anterior most part of the sperm. It contains hydrolytic enzymes that help in the penetration of the sperm through the layers of the oocyte. In case, the sperm is lacking an acrosome or has a dysfunctional acrosome, it will be capable of penetrating the corona radiata layer only.
The corona radiata layer is a cellular layer. It is situated outside the zona pellucida layer. When the granulosa cells are arranged in a layer, it is called the corona radiata layer. When the cells are scattered here and there (as in the layer outer to corona radiata), the layer is called cumulus oophorus. The sperm can penetrate in between the gaps of the granulosa cells by its drilling action. The acrosome is not required till this stage.
When the sperm reaches the zona pellucida layer, there are specific sperm receptors called ZP3 receptors, which are found on the surface of zona pellucida, and they bind to the acrosome. Binding of the acrosome to the ZP3 receptors, initiates the acrosomal reactions. But a sperm with a dysfunctional acrosome cannot bind to the zona pellucida of the secondary oocyte. Hence, no acrosomal reactions can be initiated. Sperm lysins won’t be formed. This way the sperm will be incapable of penetrating through the zona pellucida or the plasma membrane of oocyte (oolemma).