Question

In spiral cleavage, planes are:
A. Vertical
B. Horizontal
C. Subequatorial
D. Oblique

Answer 1

Hint: In development biology, cleavage is the division of cells in the early embryo.It leads to formation of blastomere. The cycle follows fertilization, with the exchange being set off by the activation of a cyclin-dependent kinase complex.

Complete answer:
- Depending upon the amount of yolk in the egg, the cleavage can be holoblastic (aggregate or whole cleavage) or meroblastic (incomplete cleavage). The pole of the egg with the highest concentration of yolk is alluded to as the vegetal pole while the opposite is alluded to as the animal pole. The plane of cleavage can be-
- The spiral cleavage is the common type of development in the early embryo. In this process division of the embryo occurs and the cells form a spiral around the pole to pole axis of the embryo. In this the planes of the cleavage are oblique.
- The vertical cleavage occurs when a furrow does not pass through the median axis from the animal pole towards the opposite pole.
- Horizontal plane cleavage, the furrow runs through the cytoplasm through the equatorial plane.
- Sub Equatorial plane cleavage is the cleavage where the line dives the eggs halfway between the animal pole and the vegetative pole.

Hence the correct answer is option D.

Note: Cleavage varies from different types of cell division in that it increases the quantity of cells and atomic mass without increasing the cytoplasmic mass. This implies that with each progressive subdivision, there is generally a larger portion of the cytoplasm in each daughter cell than before that division, and in this way the ratio of nuclear to cytoplasmic material increases.