5.1.2

The Cell Cycle

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The Cell Cycle

We have already seen that not all cells can divide (e.g. viruses need a host cell to divide). Eukaryotic cells that have the ability to divide have a cell cycle.

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The cell cycle

  • Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division.
    • This is called the cell cycle.
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Phases of the cell cycle

  • The cell cycle has two major phases: interphase and the mitotic phase.
    • During interphase, the cell grows and DNA is replicated.
    • During the mitotic phase, the replicated DNA and cytoplasmic contents are separated, and the cell divides.
  • There are two types of cell division in eukaryotes: mitosis and meiosis.
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Interphase

  • Interphase is subdivided into three growth stages called G1, S and G2 stage.
    • In G1, the cell grows.
    • In S, DNA synthesis happens.
    • In G2, the cell grows some more before the mitotic phases begins.
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The mitotic phase

  • Mitosis is the part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication.
  • Multicellular organisms go through mitosis to grow and repair damaged tissues.
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Regulation of the cell cycle

  • Internal checkpoints are important in the regulation of the cell cycle.
    • At the first checkpoint (G1), DNA is checked to make sure there is no damage and the cell is checked to see if it is the correct size and has enough energy reserves.
    • At the second checkpoint (G2), chromosomes are checked to make sure that they have all been replicated and none of the duplicated DNA is faulty.
    • At the third checkpoint (M), sister chromatids are checked to confirm that their attachments to the spindle are suitable.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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