Continuity of cells

The cell cycle

Actively dividing eukaryotic cells pass through a series of stages known collectively as the cell cycle:

  • Interphase - two growth or gap phases (G1 and G2) separated by a synthesis (S) phase
  • Mitosis - a nuclear division during which the chromosomal material is partitioned into daughter nuclei
  • Cytokinesis - the cell divides into two daughter cells


An intense period of metabolic activity as the cell synthesises new components such as organelles and membranes, new proteins and DNA.

  • G1 phase - synthesis of macromolecules occurs and volume of cytoplasm and number of organelles increase rapidly
  • S phase - DNA duplicated and amount of chromatin doubled. Histones form
  • G2 phase - spindle proteins (tubulin) synthesised



  • chromatin condenses to form chromosomes
  • in animal cells - centrioles move to opposite poles
  • spindle begins to form
  • as chromosomes continue to condense, they…


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