1.2.2 Mitosis and the cell cycle

• Why is cell division by mitosis important?

  ● Parent cell divides to produce 2 genetically identical cells for...

  ○ Growth and development of multicellular organisms

  ○ Replacing (worn out or damaged) cells → repair damaged tissues
• Describe the stages of the cell cycle, including mitosis

  Cell cycle = series of stages in which a cell divides (DNA is doubled then divided into 2 identical cells)

  Stage 1

  ● DNA replicates to form 2 copies of each chromosome

  ● Cell growth - number of sub-cellular structures increases such as ribosomes / mitochondria

  Stage 2

  (mitosis)

  ● One set of chromosomes is pulled to each end of cell

  ● Nucleus divides to form two nuclei

  Stage 3

  ● Cytoplasm and cell membrane divide

  ● 2 genetically identical cells are formed
• why is this statement wrong?

  “DNA divides before mitosis.”

  DNA has to replicate / double before mitosis, so that new cells formed can each have the same number of chromosomes as the original cell.
• why is statement wrong?

  “Mitosis repairs cells.”

  Mitosis creates new cells to replace damaged or dead ones, therefore

  repairing the tissue (group of cells) but not the cells themselves.
• Give examples of contexts where mitosis is occurring

  ● Regular replacement of skin cells, blood cells, cells lining digestive

  system

  ● Growth of embryos into foetuses and beyond

  ● Plant root / shoot tips