Which of the following does not belong to cleavage? A) Decrease in size of blastomere B) Rapid mitotic division C) Interphase of short duration D) Differentiation of blastomere?

Question

Answer

Correct option is d.. Blastomeres do not differentiate during cleavage.

Answer

After fertilization, the zygote will begin to undergo development. This single cell will eventually give rise to every cell that will make up the person it will develop into. During the first four days after fertilization, the stage known as cleavage, the principle developmental mechanism that is being employed is (rapid) cell division, or (rapid) mitosis (with a very reduced or short interphase). The process of cleavage involves a series of cell divisions that are not accompanied by any growth. Essentially what is occurring is that the relatively large zygote is subdivided into a number of smaller cells, whose combined size is approximately the same as the zygote. During this time, approximately five cell divisions occur, resulting in 32 cells. These 32 cells are essentially identical to one another and are all clustered together in a single mass. This mass of cells is called as the morula, which literally means little mulberry and is based on the clustered appearance of the cells at this stage. This process is fueled by nutrients present in the original oocyte. These nutrients are not sufficient, however, as a supply for the entire developmental process. To obtain nutrients to support subsequent development, the pre-embryo will ultimately have to attach to the mother.

Thus, the correct option is (D).

Answer

Understanding Cleavage in Embryonic Development
Cleavage refers to the early stages of embryonic development where a single fertilized egg (zygote) undergoes a series of rapid cell divisions. Among the options given, one does not belong to the process of cleavage.
Options Analysis
- A) Decrease in size of blastomere
- During cleavage, the size of individual cells, known as blastomeres, does not decrease. Instead, the overall size of the embryo remains relatively constant while the number of cells increases.
- B) Rapid mitotic division
- Cleavage is characterized by rapid mitotic divisions leading to an increase in cell number. This is a defining feature of the cleavage process.
- C) Interphase of short duration
- In cleavage, the interphase, the phase of the cell cycle where the cell prepares for division, is indeed of short duration. This allows for the rapid succession of cell divisions.
- D) Differentiation of blastomere
- Differentiation refers to the process where cells begin to specialize and take on specific functions. This does not occur during the cleavage stage; differentiation typically happens later in development.
Conclusion
The option that does not belong to cleavage is D) Differentiation of blastomere. Cleavage is focused on cell division and not on the specialization of cells. Understanding this distinction is crucial in the study of embryology and developmental biology.

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