Explain how the process of DNA replication ensures that each daughter cell produced by mitosis receives a complete and identical set of genetic information.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
DNA replication occurs during interphase (S phase) before mitosis begins.
Each strand of the double helix acts as a template, producing two identical double‑stranded DNA molecules (semi‑conservative replication).
As a result, sister chromatids are formed; they are held together at the centromere and are genetically identical.
During mitosis the sister chromatids are separated and pulled to opposite poles, so each daughter cell receives one copy of every chromosome, giving both daughter cells an identical, complete genome.
Each strand of the double helix acts as a template, producing two identical double‑stranded DNA molecules (semi‑conservative replication).
As a result, sister chromatids are formed; they are held together at the centromere and are genetically identical.
During mitosis the sister chromatids are separated and pulled to opposite poles, so each daughter cell receives one copy of every chromosome, giving both daughter cells an identical, complete genome.
Examiner tips
- State the timing of replication (S phase).
- Explain semi‑conservative mechanism and sister chromatid formation.
- Show that chromatids separate to give identical genomes.
- Use terms: template strand, centromere, identical genome.
Common mistakes
- Confusing meiosis with mitosis.
- Lacking detail on semi‑conservative replication.
Mark scheme (4 marks)
- DNA replication occurs during interphase (S phase) before mitosis begins
- Each strand of the double helix acts as a template, producing two identical double-stranded DNA molecules (semi-conservative replication)
- As a result of replication, sister chromatids are formed, which are held together at the centromere and are genetically identical
- During mitosis, sister chromatids are separated and pulled to opposite poles so that each daughter cell receives one copy of every chromosome, giving both daughter cells an identical, complete genome
Key terms in this question
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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