mitosis

• Multicellular eukaryotic organisms require a continuous supply of new cells for growth, development and repair
• The process through which these cells are generated is known as the cell cycle
• Cell cycle

  1. Growth

  2. DNA replication

  3. Mitosis and division (cytokinesis)
• DNA

  When a cell is not dividing, it is spread out in long strings; when preparing for division, it condenses into chromosomes
• Chromosomes

  • Packets of condensed DNA
  • Each chromosome contains a large number of genes that control the development of different characteristics
• Humans have 23 pairs of chromosomes, for a total of 46 chromosomes
• Chromosome duplication

  Each chromosome duplicates, with the duplicate staying attached to the original chromosome, forming an X-shape
• The resulting daughter cells can then contribute to growth, development or repair and undergo the cell cycle all over again
• Cytokinesis (Cell division)


  The cytoplasm divides in a process known as cytokinesis. This produces two daughter cells that are genetically identical to one another.
• Cell cycle

  Cellular growth - the cell gets larger and produces more sub-cellular structures, such as mitochondria and ribosomes.

  DNA replication - chromosomes duplicate, each consisting of two arms (copies).

  More cell growth.

  Mitosis - the DNA divides into two.

  Cytokinesis - the cell divides into two
• Are the cells created by mitosis genetically identical to each other, or genetically different?

  Genetically identical
• Which stage of mitosis involves centromeres dividing to pull chromatids apart?

  Anaphase
• A gene


  a short section of DNA that codes for a protein and as a result controls a

  characteristic- therefore each chromosome carries many genes.
• The nucleus contains 


  genetic information
• What form is the nucleus' genetic information found?

  The form of chromosomes, which contain coils of DNA.
• Gamete


  Sex cell, Haploid number of Chromosomes
• Why is mitosis important?

  In multicellular organisms, it is important in their growth and development, and when replacing damaged cells.
• Why is mitosis important in asexual reproduction?

  This type of reproduction only involves one organism, so to produce

  offspring it simply replicates its cells.
• Interphase


  • This is the initial growth phase. Extra ribosomes, mitochondria and other sub-cellular structures are produced.
  • The cell’s chromosomes (which are made of DNA) are replicated (copied) so that there are two sets of the cell’s chromosomes.
• Prophase


  • Chromosomes condense (coil-up tightly).
• Metaphase


  • Chromosomes line-up along the middle of the cell.
• Anaphase


  • The two sets of chromosomes are pulled to opposite ends of the cell by cell fibres
• Telophase


  • The nucleus splits and two new nuclei (plural of nucleus) form.
• Mitosis ensures that both daughter cells have the same chromosomes as each other and the parent cell.

  • This is important for processes that require identical cells to be produced.
  • For example, the growth and repair of tissues and asexual reproduction.