THE MITOTIC CELL CYCLE (Topic 5)

• The role of ​mitosis and the cell cycle ​is to produce ​identical daughter cells for growth and asexual reproduction​ ​of cells
• All the cells produced by mitosis are ​genetically identical therefore ​mitosis does not give rise to genetic variation​
• Mitosis is important for:

  • Growth
  • Replacing ​dead or damaged cells
  • Repairing ​damaged tissue (via cell replacement)
  • Asexual reproduction
• 1. Telomeres ​prevent genes from being lost during the process of DNA replication
• During the cell cycle, a cell is formed, it grows and then divides to form daughter cells. There are three stages of the cell cycle:

  1. interphase
  2. mitosis
  3. cytokinesis
• Interphase​ – to summarise, during this stage, the cell ​grows and then prepares to divide​ – ​chromosomes and some organelles are replicated, and chromosomes also begin to condense. Interphase consists of the G1, G2 and S phases.

  o G1​ - the cell receives a signal committing the cell to replicate DNA, the cell grows and prepares to enter the S phase

  o S ​- the genome is completely duplicated

  o G2​ - G2 - prepares for mitosis
• Mitosis​ ​– mitosis is a form of cell division that produces identical cells, there are four stages of mitosis: ​prophase, metaphase, anaphase and telophase
• Cytokinesis​ ​– during cytokinesis, the parent and replicated organelles move to opposite sides of the cell and the ​cytoplasm divides​ ​thus producing two daughter cells
• Stem cells:

  Cells produced by mitosis are undifferentiated (those are called stem cells) which can be made into ​specialised cells​ via differentiation. Stem cells repeatedly undergo cell division and are used for cell replacement and tissue repair. Once the cell becomes specialised for a specific function it stops dividing.

  However, if cell division is ​uncontrolled ​this can lead to the formation of a mass of cells called a ​tumour​, which can cause ​cancer,