Mitosis is a kind of somatic cell division in which the mother nucleus (n or 2n) divides into two daughter nuclei passing through a series of complicated changes and each newly formed daughter nucleus bears the same number of chromosomes and unchanged properties as its mother cell.
Strictly speaking cell division refers to the division of nucleus alone.
Mitosis takes place in the somatic cells of plants, such as-
i. At the tip of branches.
ii. At the tip of growth region of root.
iii. To the surrounding area of dicot plant for growth of circumference,
iv. To recover the injured places.
Mitosis is a continuous process for the convenience of description, it is divided into following five phases:
i. Prophase.
ii. Pro-metaphase.
iii. Metaphase.
iv. Anaphase.
v. Telophase
Characteristics of mitosis:
i. Each chrothosOme divides vertically into two daughter chromosomes (chromatids). Each of the two newly formed daughter chromosomes reaches to opposite poles producing two daughter nuclei. So chromosomal number remains same in each of the two daughter nuclei.
ii. The daughter cells have the same properties of their mother cells.
iii. Chromosomal number for both daughter cells and mother cell remain equal.
iv. The daughter cell grows to become more or less similar in volume.
The significances of Mitosis are as follows:
1) To keep balance between nucleus and cytoplasm: The balance between nucleus and cytoplasm is maintained through mitosis so that the shape and size of the cell remain unchanged.
2) Physical growth: in multi-cellular organisms a one celled zygote turns into a many celled embryo. Repeating the same process the embryo eventually forms the multi-cellular organism.
3) Formation of reproductive organs: By equational division, reproductive organs are formed in the multi-cellular organism.
4) Reproduction: In Eukaryotic organism, reproduction occurs by, this process. (such as in chlamyclomonas)
5) Keeping the chromosome number constant: mitosis ensures the quantitative and qualitative distribution of chromosomes in all the cells of an organism.
6) Repairing of wounds: Any wounds or broken parts of the organisms can be repaired rapidly by mitosis.
7) Demerits of mitosis: Tumour, cancer, etc. are caused by uncontrolled mitosis.
Mitosis means equational division, because:
i) The chromosomal number and properties of the two daughter cells newly formed from one cell remain similar to their mother cell.
ii) Each of the daughter cells again divide and give rise to two daughter cells. In this case, the daughter cell also bears same characteristics of its mother cell.
iii) As mitosis occurs in somatic cells, it goes on repeatedly up to the full development of the organism without any change of characteristics of the mother cell.
On the basis of the characteristics mentioned above mitosis is also called equational division.
