Question

The fifth cleavage of the fertilized egg of frog results in the formation of
A. 16 cells
B. 48 cells
C. 64 cells
D. 32 cells

Answer 1

Hint: After fertilization, cleavage occurs which is a type of division not as same as a simple division/mitosis. The cleavage in the frog is holoblastic. Such type of cleavage furrowed the egg cell and results in unequal cells.

Complete answer: The cleavage in the frog is latitudinal. The first cleavage will result in the formation of 2 cells which is known as meridional. The second cleavage will result in the formation of 4 cells (as the divisions are latitudinal) which is also known as meridional which is followed by 8 cells latitudinal cleavage, 16 cells, and the fifth cleavage will result in the formation of 32 cells which is called a blastomere. The final stage is called a morula. There are 12 cleavages in the frog. It has been observed that at 12th cleavage the blastula possesses about 4096 cells. The blastula moves to the next stage, namely gastrulation at a stage in which it has about 20,000 cells.
Hence, the correct answer is option D, i.e., 32 cells

Note: The fifth (also double) cleavage which would have an embryo of 32 cells is more likely to be out of order, and the symmetry and regularity of the earlier cleavages are missed. The gradient of cleavage levels from the fast-dividing blastomeres of the animal hemisphere to the gradually dividing cells of the vegetal hemisphere is now becoming more evident.