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PinkMonkey Online Study Guide-Biology
CHAPTER 6 : CELL DIVISION
6.0 Introduction
The cell is the structural and functional unit
of life. New cells arise from the preexisting ones. The process by which
new cells are formed from the pre-existing cells is called cell division.
In unicellular organisms, the cell division directly produces two individuals and thus, represents a type of reproduction (multiplication).
In multicellular organisms, there are two types of cells;
the somatic cells or the body cells (which form the body of the
organism) and the reproductive cells (such as gamete-producing cells
and-spore producing cells).
The somatic cells divide by mitosis (equational division) and the reproductive cells divide by meiosis (reduction division). Mitosis helps in growth and development of an organism. Meiosis produces gametes in sexual reproduction and spores in asexual reproduction.
All eukaryotic organisms, plants as well as animals, show great regularity as well as similarity in the cell divisions. Generally, a cell increases in size before dividing. This is mainly due to the synthesis of proteins, RNA and DNA. This is followed by division of the cell nucleus (karyokinesis) and finally the division of the cell cytoplasm (cytokinesis). All these events collectively form a cell cycle.
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