Question

Vegetal hemisphere of frog’s egg has
A. Germinal vesicle
B. Yolk
C. Pigment
D. Grey crescent

Answer 1

Hint: An embryo is divided into two hemispheres as the animal pole and the vegetal pole in a blastula. The lower end of the embryo is called the vegetal pole. It is made up of larger, yolk type cells that divide and grow more slowly.

Complete answer:
- The vegetal pole consists of big yolky cells that separate very slowly that is different with the animal pole above it.
- The growth of the animal-vegetal axis takes place earlier to fertilization. Sperm can enter anywhere in the animal hemisphere.
- The location of sperm entry indicates the dorso-ventral axis - cells opposite the portion of sperm entry will finally take the dorsal portion of the body.

Now, let us find the solution from the option.
- The embryo is usually separated into two poles, they are- the animal pole and the vegetal pole.
- The vegetal pole in the frog contains yolk but the animal pole consists of melanin granules due to which it is dark in colour.
- The grey crescent is present in between the animal pole and vegetal pole.

Thus, the correct option is B. i.e. Yolk.

Note: In the frog Xenopus laevis, a pigment pattern provides the oocyte with characteristics of a spirally symmetrical body with a distinct polarity. The vegetal hemisphere is weakly pigmented and the animal hemisphere is dark brown in color. The symmetry axis goes through on one part the animal pole, and on the other part the vegetal pole. The two hemispheres are divided by an un-pigmented central bar.