Cell cycle

The life of a cell can be represented by the cell cycle. The cell cycle consists of various phases these include G1, S, G2, M and cytokinesis stages. The cell cycle is described as being a “cycle” on the basis that there is no beginning or ending, and cells are continually entering and exiting at various phases of the cycle.

Phases of the cell cycle

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Interphase

Interphase is the broad term used to the phases that occur prior to the M phase, and hence comprises of the G1, S and G2 phases. Interphase occurs prior to mitosis and is where the cell spends most of it’s life.

G1 Phase

  • During G1 the cell doubles in size and its organelles, enzymes and other molecule increase in number.
  • Cells spend most of their time in this phase.

S phase

  •  The S phase is known as the synthesis phase and is the phase whereby DNA replication occurs.

G2 phase

  • During G2 structures required for cell division begin to assemble.
  • G2 marks the beginning of chromosome condensation.

M phase

The phase is the part of the cycle where mitosis or meiosis occurs.

Cytokinesis

This is the step preceding nuclear division and refers to the physical division of the cell’s cytoplasm to form distinct cells.

  • Cytokinesis is not part of the mitotic cycle but is considered a separate step.
  • In animals cells a cleavage furrow is formed used to divide the cells.
  • In plant cells vesicles join together to form a cell plate that allows for the constriction of the cells.
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Newly produced cells have the option to continue growing and reproducing again. Alternatively, after leaving the cell cycle they may differentiate and specialise forming specific functions within the organism that goes on to age and die.

See also


  1. http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells2.html 

  2. https://www.boundless.com/biology/textbooks/boundless-biology-textbook/cell-reproduction-10/the-cell-cycle-88/the-mitotic-phase-and-the-g0-phase-396-11622/