Mitosis (Cambridge (CIE) AS Biology): Revision Note

The importance of mitosis

• Mitosis is the process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent nucleus

• The process of mitosis is of great biological significance and is fundamental to many biological processes:

Growth of multicellular organisms

• The two daughter cells produced are genetically identical to one another (clones)

• They have the same number of chromosomes as the parent cell

• This enables unicellular zygotes (as the zygote divides by mitosis) to grow into multicellular organisms

• Growth may occur across the whole body of the organism or be confined to certain regions, such as in the meristems (growing points) of plants

Replacement of cells & repair of tissues

• Damaged tissues can be repaired by mitosis followed by cell division

• Dead and damaged cells need to be continually replaced by genetically identical cells

  • In humans, for example, cell replacement occurs particularly rapidly in the skin and the lining of the gut

Asexual reproduction

• Asexual reproduction is the production of new individuals of a species by a single parent organism

  • The offspring are genetically identical to the parent

• For unicellular organisms such as Amoeba, cell division results in the reproduction of genetically identical offspring

• For multicellular organisms (as seen with many plant species) new individuals grow from the parent organism (by cell division) and then detach (‘bud off’) from the parent in different ways

  • Some examples of these are budding in Hydra and yeast and runners from strawberries