It is a type of cell division in which the number of chromosomes in daughter cell remains constant as in mother cell. It is also known as somatic cell division or somitogenesis. The process of mitosis is almost similar in both animal and plant that take place during embryonic development and growth. Although mitosis is a continuous process, for better understanding it can be divided into two phases, namely Karyokinesis and Cytokinesis.
KARYOKINESIS: it is the division of the nucleus, which involves further four stages or phases:
- Prophase: prophase includes the following characters:
- During early stages of cell cycle, chromosomes are not clearly visible even under the electron microscope.
- As prophase proceeds, fine threads of chromosomes appear in form of network called chromatin
- Later on, chromosomes get condensed and become more visible having two chromatids attached at the point called centromere.
- In the late prophase, nuclear membrane starts to disappear and nucleolus also disappears.
- Finally, all the nuclear material gets free in the cytoplasm and mitotic apparatus start to originate. Aster and spindle collectively called Mitotic apparatus. It contains different types of fiber: Continuous Fibers are the fibers which run from pole to pole; Discontinuous Fibers are those fibers which run from central region or central poles; Astral Fibers are those fibers are short radiating from centrioles and remain at the pole.
- Metaphase: Metaphase have following features:
- In the beginning of this stage, nuclear membrane is completely disappeared and nuclear material arranged themselves in cytoplasm.
- In this phase, chromosomes become more prominent and the region of centromere known as Kinetochore appeared with the special fibers known as kinetochore fibers.
- The chromosomes arrange themselves on equatorial plane with spindle fiber radiating from poles.
- The spindle fiber that attached with kinetochore, start to contact and move towards the pole.
- As the result of contraction, chormatids become detached at the point of centromere and now served as chromosomes.
- At the end, chromosomes pulled to the opposite poles by further contraction of fiber.
- Telophase: This is the last phase of karyokinesis and is known as reverse of prophase. It has following main features
- Chromosomes start to coiling and forming chromatin network. In the late telophase, two-daughter nuclei are formed.
- Nuclear membrane is reappeared and nucleolus and other organelles start to reapper.
CYTOKINESIS: It is the division of cytoplasm, as a result of which two daughter cells are formed
- During late teleophase, the astral microtubules end signals to equatorial region of cell.
- At this point, actin and myosin are activated that form contractile ring.
- Later on cleavage, furrows developed at the center that deepens towards the center of the cell and finally two daughter cell are formed.
As a result of mitosis, two daughter diploid cells arise from the division of diploid mother cells.