During the cell cycle, a cell undergoes interphase before mitosis begins. Explain what happens during interphase and during mitosis to ensure that two genetically identical daughter cells are produced.

Pearson Edexcel A-Level Biology A (9BI0) — 2.2 Cell cycle and mitosis · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

During interphase the cell grows and synthesises new organelles, preparing for division. DNA replication occurs in the S‑phase, so each chromosome is copied and becomes a sister chromatid pair.

In mitosis, during metaphase the duplicated chromosomes line up at the cell equator. In anaphase the spindle fibres shorten, pulling the sister chromatids apart to opposite poles. Finally, cytokinesis divides the cytoplasm, producing two genetically identical diploid daughter cells.

Examiner tips

  • Use the term 'interphase' and mention growth and organelle synthesis; include 'DNA replication' and 'sister chromatids'. Describe metaphase alignment and anaphase separation clearly. Finish with cytokinesis producing identical diploid cells.
  • common_mistakes
  • :
  • Forgetting to mention DNA replication during interphase. Confusing mitosis with meiosis or omitting cytokinesis. Using vague terms like 'cell division' instead of specific stages.

Mark scheme (5 marks)

  1. During interphase, the cell grows / new organelles are synthesised
  2. During interphase, DNA replication occurs so each chromosome is copied
  3. During metaphase, chromosomes align at the cell equator
  4. During anaphase, spindle fibres pull chromatids to opposite poles of the cell
  5. Cytokinesis divides the cytoplasm to produce two genetically identical diploid daughter cells

Key terms in this question

cell cycle · interphase · mitosis

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