Question
Biology Question on Structural Organisation of Animals and plants
Grey crescent is the area
A
at the point of entry of sperm into ovum
B
just opposite to the site of entry of sperm into ovum
C
at the animal pole of the egg
D
at the vegetal pole of the egg.
Answer
just opposite to the site of entry of sperm into ovum
Explanation
Solution
In ovum of some amphibians, about ten minutes after the penetration of sperm, the yellow cortical ooplasm of the egg starts flowing towards the sperm entrance. At the future dorsal side, the cytoplasm moves towards the animal pole, and at the opposite side (the future ventral side) it moves towards the vegetal pole. This exposes a lightly pigmented crescent-shaped area of marginal cytoplasm on the dorsal side, exactly opposite the point of sperm entrance. This is known as grey crescent.