Question

Gray crescent structure is found in
A) Eye of cockroach
B) Eye of frog
C) Brain of rabbit
D) Fertilised egg of frog

Answer 1

Hint:Grey crescent is the cortical region formed in the egg of frog just after Fertilisation has occurred which is seen located at the opposite side from the entry side of sperm.

Complete answer:
During the development of frog or during the course of Fertilisation event in frog there are several changes with an egg undergoes after there is interaction with sperms. Germ cells undergoes second round of meiosis and functional gamete are formed where the cytoplasm of egg rotates 30 degrees from poles, this rotation is clearly indicated by the presence of light colluded band called as gray crescent, this is the region where there is maximum deposition of cortical granules which are nothing but proteins.

This band is always seen at the side opposite to the side of entry of sperm to egg. Gray crescent is not seen in the Eye of cockroach since the cells which are determined to form eye cells are not germ cells. It is not present in the eye of a frog and also not found in the brain of a rabbit. This gray crescent fades gradually as the zygote undergoes division and forms a mass of cells in the later stages of development.

Hence, the correct answer is option D.

Note:Gray crescent is found at the middle segment of egg cells of frogs. There is an animal pole at the anterior region and vegetal pole at the posterior region of the egg.