A student claims that every body cell in a human contains identical genetic information, even though the body contains many different types of cells. Explain why this claim is correct, linking your answer to the process of mitosis.

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)

Mitosis produces two daughter cells from one parent cell. Before division, the DNA in each chromosome is copied during S phase, so each chromosome is duplicated. During mitosis, the duplicated chromosomes are distributed so that each daughter cell receives a full, identical copy of the DNA. Consequently, the number of chromosomes in each daughter cell is the same as in the parent cell – 46 in humans. As this process repeats during growth, every body cell ends up with the same genetic information.

Examiner tips

  • Use the term ‘mitosis’ and mention the two daughter cells
  • Explain DNA replication in S phase
  • State that each daughter cell gets an identical chromosome set
  • Mention the chromosome number 46

Common mistakes

  • Confusing meiosis with mitosis
  • Saying only some cells have identical DNA
  • Omitting the chromosome number 46

Mark scheme (5 marks)

  1. Mitosis produces two daughter cells (from one parent cell)
  2. DNA / chromosomes are copied / replicated before cell division
  3. Each daughter cell receives a full / identical copy of the DNA / chromosomes
  4. The number of chromosomes in daughter cells is the same as in the parent cell (46 in humans)
  5. This process is repeated as the organism grows, so all body cells end up with identical genetic information

Key terms in this question

mitosis · genetic information

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