Question

4. Discuss mitosis: Name all the stages of mitosis. Describe the main events that happen during each phase.

Answer 1

Mitosis: The process of cell division which results in the production of two daughter cells from a single parent cell. The daughter cells are identical to one another and to the original parent cell. It is also called somatic cell division. It occurs in non-reproductive cells just after the interphase resulting in the same number and kind of chromosome as their parent cell.

Stages of mitosis:

There are necessarily four phases of mitosis which are listed below with the events that happen to the cells during those phases.

1. Prophase: This is the first phase of the mitosis stage which occurs after the G2 phase of interphase. The main events that happen to cells at this phase are Condensation of the chromosome, Spindle fibre formation, Nuclear membrane disintegration and nucleolus disappearance. The centrosome starts to move towards opposite ends.

2. Metaphase: This is the second phase of the mitosis stage which occurs after the prophase of mitosis. Here, the cell membrane completely vanishes which makes the condensed chromosomes visible at the microscopic level. The chromosomes align themselves at the equatorial region of the cell(imaginary line). The spindle fibre formation is complete which ensures the proper alignment of the chromosome at the equator.

3. Anaphase: This is the third phase of the mitosis stage which occurs after the metaphase of mitosis. At this stage, the chromosome aligned at the equatorial region starts to separate as sister chromatids. They move towards the opposite side as the spindle fibre starts shortening.

4. Telophase: This is the fourth phase of the mitosis stage which occurs after the anaphase of mitosis.Here, The sisters chromatids reaches to the opposite poles after the complete shortening of the spindle fibre. The nuclear envelope or nuclear membrane starts forming again. Both sets of chromosomes start to decondense. After this phase, the cytokinesis starts.