5.1.2—Importance of mitosis

Mitosis is nuclear division that normally produces two genetically matching daughter nuclei with the same chromosome number as the parent nucleus. Cytokinesis then separates the cell around those nuclei.

• Genetic matching: DNA is copied before mitosis, and the sister chromatids are separated so each daughter nucleus receives one matching copy of the genetic information.
• Chromosome number: The chromosome number is maintained because each daughter receives one complete set corresponding to the parent nucleus; mitosis is not a reduction division.
• Growth: Repeated mitotic divisions increase cell number, allowing a multicellular organism or tissue to grow.
• Replacement: New cells replace damaged or dead cells while preserving the tissue’s usual genetic information.
• Repair: Cell division supplies replacement cells for damaged tissue; it does not reverse damage inside the original cell.
• Asexual reproduction: In organisms that reproduce asexually, mitotic descendants can remain genetically matching the parent, so one parent can produce new individuals without fusion of gametes.

Once DNA has been copied, accurate separation of the matching chromosome copies lets one daughter nucleus inherit each complete set. Cytokinesis turns the two nuclei into separate cells, so the same mechanism can add cells for growth, replace cells during turnover, repair tissue or produce a new asexual individual.

Mitosis replaces a damaged cell; it does not repair that cell by undoing its injury. “Genetically matching” describes the intended nuclear DNA outcome, while mutation or environmental effects can still create differences. The detailed G1–S–G2–M sequence belongs to card 4562.