Question

Cleavage is a unique form of mitotic cell division in that
A. The nucleus does not participate
B. No spindle develops to guide the chromosomes
C. The plasma membranes of daughter cells do not separate
D. There is no growth of cells

Answer 1

Cleavage can be defined as a rapid mitotic cell division that takes place in a zygote to develop a hollow, spherical, multicellular developmental stage which is known as a blastula. Cleavage is also known as blastulation.

Complete answer:
The cleavage simply means the division of cells that happens in the early embryo. The zygotes of many species go through rapid cell division cycles but there is no significant overall growth of cells seen. Cleavage produces a cluster of cells that are the same in size as the original zygote. The different cells obtained from cleavage are known as blastomeres and generate a compact mass which is known as the morula. Finally, the cleavage ends with the production of the blastula.
Based on the amount of yolk that presents in the egg, there are two types of cleavage which are holoblastic and meroblastic. Holoblastic cleavage refers to total or entire cleavage or and meroblastic cleavage refers to partial or incomplete cleavage. The pole of the egg which possesses the highest concentration of yolk is referred to as the vegetal pole and the opposite i.e. the pole with the lowest concentration of yolk is referred to as the animal pole.
Cleavage has some differences from other forms of cell division. In the case of cleavage, it increases the number of cells and nuclear mass but there is no increase in the cytoplasmic mass. This represents that, at each successive subdivision, the cytoplasm in each daughter cell becomes half than before that division. And in this way the ratio of nuclear to cytoplasmic material increases.
So, in the case of cleavage, which is a unique form of mitotic cell division in the early stage of the embryo, there is no growth of cells.
Thus, the right option is D.

Note: Cleavage simply defines the mitotic division of cells in the early stage of the embryo. According to amount of the yolk in the egg, cleavage can be two types; complete cleavage i.e. holoblastic, and partial cleavage i.e. meroblastic. The zygotes of different species undergo rapid cell division but there is no significant overall growth of the cell. The process of cleavage forms a cluster of cells that are the same size as the original zygote.