Q166 / 200 · NEET 2005 · Zoology
Grey crescent is the area:
- Aat the point of entry of sperm into ovum
- Correct answerBjust opposite to the site of entry of sperm into ovum
- Cat the animal pole
- Dat the vegetal pole.
Solution
Grey crescent marks the future dorsal side of the embryo. Subsequently, it was determined that the Grey Crescent is formed by the $30^{\circ}$ rotation of the fertilized egg to form a dorsal/ ventral axis. The crescent thus serves as a determinant of dorsal / ventral polarity: cells without it have no means of orientation.
Related Theory In the zygote of the frog, there are two poles present. The vegetal pole and the animal pole. These are separated by an area which is rich in melanin and is known as the grey crescent. The egg enters enter opposite to the region of sperm entry. The broadest part of the grey crescent forms the dorsal end. The grey crescent helps in establishing polarity.
Related Theory In the zygote of the frog, there are two poles present. The vegetal pole and the animal pole. These are separated by an area which is rich in melanin and is known as the grey crescent. The egg enters enter opposite to the region of sperm entry. The broadest part of the grey crescent forms the dorsal end. The grey crescent helps in establishing polarity.
Hence, the correct answer is option: 'B'.