Question

1. Explain the purpose of mitosis and describe the four stages of this process.

Answer 1

Mitosis is a type of cell division process found in eukaryotic organisms where one mother cell undergoes the process of cell division and ultimately gives rise to two daughter cells which are similar to the mother cell. In mitosis, the ploidy level of the cells remains the same i.e 2n. Mitosis is performed by the organisms to increase their growth by producing multiple exact copies of the pre-existing cells.

The process of mitosis can be divided into 4 stages, which are---

1) Prophase- At this stage, the nuclear membrane disappears and the chromatins condense. Thus, the chromosomes become visible for the first time. The chromosomes appear as thread-like.

2) Metaphase- Metaphase is the second stage of mitosis. At this phase, the chromosomes are organised at the equatorial region of the cell. Spindle fibres are attached with the centromeres of the chromosomes which help in the correct alignment of the chromosomes at the equatorial region.

3) Anaphase- It is the 3rd phase. Here, the sister chromatids are pulled apart by the action of the spindle fibres. The sister chromatids are separated and distributed equally to the two opposite poles of the cell.

4) Telophase- It is the final phase of the cell division. Here, nuclear membrane starts to reappear around the separated sets of chromosomes at the two poles. Chromosomes again start to become invisible as decondensation occurs. The cell membrane invaginates inwards( cytokinesis occurs) and after the completion of cytokinesis, two daughter cells are formed.