Question

An egg is observed to be fertilized by multiple sperms. Which of the following can be predicted about why this has occurred?

• A. The acrosomal process of the sperm could not bind to the receptors present on the egg membrane.
• B. The egg contained a diploid chromosome number.
• C. There was an abundance of calcium ions released by the egg.
• D. The egg cell was porous and this allowed the sperm to penetrate the cell at multiple locations.
• E. The cortical reaction was somehow inhibited.

Answer 1

Answer: (A)

The acrosomal process of the sperm could not bind to the receptors present on the egg membrane.

Polyspermy is described as an egg fertilized by more than one sperm. During fertilisation, when the sperm approaches the ovum, there occurs acrosomal reaction wherein the acrosome of sperm binds to the receptors present on the egg membrane and fuse with the outer layer of the egg (Zona pellucida). This reaction leads to fusion of male and female gametes i.e. fertilisation. The acrosome reaction renders the egg unable of polyspermy i.e. once one sperm enters the egg, the zona pellucida becomes refractory to sperm binding and penetration by undergoing cortical reaction.

If in any case egg gets fertilised by multiple sperms, then it can be said that the acrosomal reaction went wrong i.e. the sperm could not bind to the receptors present on the egg membrane, which will make the egg open to multiple sperm fertilisations.