A skin cell from a human contains 46 chromosomes. Explain what happens to the genetic material in this skin cell during mitosis, and describe the characteristics of the two daughter cells produced.

AQA A-Level Biology (7402) — 3.2.2 Cell Replication · 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 mitosis the DNA is first replicated in interphase, so the cell contains two identical copies of each chromosome (92 chromatids) before division.
The replicated chromosomes are then aligned, condensed and separated, being pulled to opposite poles of the cell.
The cell finally divides (cytokinesis) to give two daughter cells.
Each daughter cell receives 46 chromosomes, the same number as the parent, and is genetically identical to the parent cell.

Examiner tips

  • Use the term "replicated" for DNA copying; mention 92 chromatids before division. Explain separation to opposite poles and cytokinesis. State that each daughter cell has 46 chromosomes and is genetically identical.

Common mistakes

  • Confusing mitosis with meiosis; mentioning reduction of chromosome number. Failing to state that the daughter cells are genetically identical. Omitting the step of chromosome replication before division.

Mark scheme (5 marks)

  1. The DNA / chromosomes are copied / replicated before division
  2. The cell now contains two copies of each chromosome / 92 chromosomes in total before division
  3. The chromosomes are separated / pulled to opposite ends / poles of the cell
  4. The cell divides to produce two daughter cells
  5. Each daughter cell contains 46 chromosomes / the same number of chromosomes as the parent cell AND is genetically identical to the parent cell

Key terms in this question

mitosis · chromosome · daughter cell

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