1
Question
Which of the following prevents more than one sperm from penetrating a human oocyte?
Which of the following prevents more than one sperm from penetrating a human oocyte?
Open in App
Solution
The correct option is D Interaction of cortical chemicals with zona pellucida
The entry of multiple sperms into the oocyte is known as polyspermy. Ovum generally prevents polyspermy and allows only one sperm to enter and participate in fertilisation.
Polyspermy is pervented either by fast block to polyspermy and slow block to polyspermy. In the slow block to polyspermy, there are cortical enzymes released during cortical reactions. These chemicals interact with the zona pellucida layer and harden it. They also inactivate the sperm receptors.
In the fast block to polyspermy, the plasma membrane of the oocyte is depolarised by the increase in permeability to sodium ions. These changes prevent polyspermy.
The vitelline membrane encloses the oocyte and corresponds to the plasma membrane of an ordinary cell. In other words, the plasma membrane of an egg can also be referred to as the vitelline membrane. Vitelline membrane, by itself, cannot block polyspermy.
The development of the fertilisation cone takes place at the site of fusion of the plasma membranes of the sperm and oocyte. This process leads to the initiation of methods to block polyspermy, but it is not such a method itself.
Human eggs are alecithal, meaning, they are devoid of yolk. Yolk is the nutritive portion of the egg which mainly provides food for the development of the growing embryo. Yolk is usually found in the eggs of animals which lay eggs (oviparous). But in case of humans, the growing embryo derives its nourishment from the mother directly, so yolk is not required for nutrition in such eggs. Condensation of egg yolk plays no role in preventing polyspermy.
The entry of multiple sperms into the oocyte is known as polyspermy. Ovum generally prevents polyspermy and allows only one sperm to enter and participate in fertilisation.
Polyspermy is pervented either by fast block to polyspermy and slow block to polyspermy. In the slow block to polyspermy, there are cortical enzymes released during cortical reactions. These chemicals interact with the zona pellucida layer and harden it. They also inactivate the sperm receptors.
In the fast block to polyspermy, the plasma membrane of the oocyte is depolarised by the increase in permeability to sodium ions. These changes prevent polyspermy.
The vitelline membrane encloses the oocyte and corresponds to the plasma membrane of an ordinary cell. In other words, the plasma membrane of an egg can also be referred to as the vitelline membrane. Vitelline membrane, by itself, cannot block polyspermy.
The development of the fertilisation cone takes place at the site of fusion of the plasma membranes of the sperm and oocyte. This process leads to the initiation of methods to block polyspermy, but it is not such a method itself.
Human eggs are alecithal, meaning, they are devoid of yolk. Yolk is the nutritive portion of the egg which mainly provides food for the development of the growing embryo. Yolk is usually found in the eggs of animals which lay eggs (oviparous). But in case of humans, the growing embryo derives its nourishment from the mother directly, so yolk is not required for nutrition in such eggs. Condensation of egg yolk plays no role in preventing polyspermy.
Suggest Corrections
0
Similar questions
View More
Join BYJU'S Learning Program
Explore more
Join BYJU'S Learning Program
