An ordered sequence of events which involves the cell growth and division of cells is the cell cycle. The outcome of this process is the production of two new daughter cells. Cell division enables distribution of identical genetic matter to the daughter cells. Growth is an aspect seen as a consequence of the cell division process. As a result, there is an increase in the volume of the outer membrane and its enlargement. Absence of active cell division may lead to non-functioning and destruction eventually.
Those cells which are on the path of cell division advance via a series of periodic events and controlled phases of growth, division producing two identical cells and replication of DNA. This cycle involves two main stages – the interphase and the mitotic phase. Replication of DNA and cell growth takes place in the interphase whereas in the mitotic phase, the DNA that is replicated and the contents of the cytoplasm are drifted causing the cell to divide.
Also see: How do cells produce new cells?
Every sexually reproducing entity begins life as a zygote (fertilized egg), foetus. Millions of cell divisions occur as a result in a regulated environment so as to give rise to a multicellular entity. Hence, it is safe to say that one single cell forms the origin of every other cell of the body.
Upon complete development and full growth, cell division still is a necessity for the regeneration of tissues, repair (bone marrow makes new blood cells) in case of injury or replacement. A good example is the constant production of blood cells and skin cells. All of the multicellular entities adapt cell division to grow, maintain and repair tissues and cells.
The whole process of cell division is a highly regulated phenomena as the infrequent disruption in this regulation can pose some serious life-threatening outcomes. On the other hand, the unicellular entities use the mechanism of cell division to reproduce. For example – Amoeba.
While almost all body cells undergo cell division, there are some cells which do not undergo the cell division process. Those that regularly divide are the somatic cells. These are basic cells of the body. All the human cells of the body, exception being germ cells are somatic cells. Germ cells are the sex cells (eggs in case of females and sperms in case of males). Consequently, cell division produces progeny from some multicellular entities, such as those plants growing from cutting.
These somatic cells comprise two copies each of chromosomes from their parents (i.e., one copy from each of their parents). In the lifespan of a human being, cells in the body replace themselves.
To summarize, cell division is a means of reproduction in unicellular entities which occurs through means such as binary fission. Whereas in multicellular entities, the process of cell division enables the production of new cells (example blood cells), formation of gametes (sex cells), fusion of which causes the formation of sexually reproduced organisms. In order for cells to grow after cell division in living entities, there must be a steady increase in the number of cells, which is contributed by the process of cell division. This increase must be until they reach their maximum size. Additionally, when the body is under repair as a result of any injury etc, cell division plays a pivotal role in healing and substituting the lost cells by producing new cells.
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