Question

Explain mitosis with a neat labelled diagram.

Answer 1

Hint: Mitosis is the stage in the cell cycle in which the newly formed DNA splits and two new cells are formed with the same number and type of chromosomes as the nucleus of the parent cell. Mitosis is an asexual reproduction mechanism found in single-celled species.

Complete answer: Mitosis is a form of cell division in which two haploid or diploid daughter cells divide into a single haploid cell (n) or diploid cell (2n) that are the same as the parent cell. In somatic cells of plants and animals, mitosis occurs. The two daughter cells in this division have the same number of chromosomes as those in the parent cell.

Four essential phases of mitosis consist of mitosis: prophase, metaphase, anaphase, and telophase.
A) Prophase: In karyokinesis, it is the first visible step. The chromosomes appear as chromatids which are long coiled threads. Due to the condensation of DNA, the chromatin becomes shorter, thicker and visible. Now those chromatins are called chromosomes. Each chromosome begins to split into two sister chromatids in the longitudinal direction. These sister chromatids, at the centromere, are bound to each other. The nuclear membrane and the nucleolus start to disappear in this phase and will gradually disappear completely.
B) Metaphase: The nuclear membrane and nucleolus vanish completely and the spindle fibres appear simultaneously. Spindle fibres are connected to a chromosome's centromere. On the equatorial plane, the chromosomes are arranged, systematically. The method of collecting chromosomes in the equator is called congression, and the metaphase plate is called the plate-shaped.
C) Anaphase: Each chromosome splits into two sister chromatids and forms two daughter chromosomes. Owing to the contraction of spindle fibres and stretching of interzonal fibres, the daughter chromosomes are pushed towards the poles. The chromosomes display distinct shapes during polar motion, i.e. in appearance, J, U, V, L or I are formed. Each pole will get one set of daughter chromosomes at the end of anaphase. It is the shortest stage and is often referred to as the migratory stage.
D) Telophase: Chromosomes of the daughter meet the corresponding poles, uncoil and become small, long and clear. The fibres of the spindle begin to disappear and gradually vanish. Reappearing of the nuclear membrane and the nucleolus can be witnessed. At the end of telophases, two nuclei are produced. The nuclei have the same chromosome number as that of the parent cell. It is the last apparent step of karyokinesis and is often referred to as the stage of reorganisation. Mitosis is accompanied by Cytokinesis or cytoplasm splitting.

Note: The cell spends most of its life in the interphase, which is the immediate phase before the prophase, where preparations are made before mitosis commences (the DNA is copied). Prophase is theoretically the first stage of this process. Metaphase is preceded by prometaphase when the cycle is studied in more detail.