# Explain how DNA replication during S phase ensures that each daughter cell produced by mitosis receives a complete and identical copy of the genome.

> IB DP Biology Higher Level (2023 syllabus) — D2.1 Cell and nuclear division · Explain · 4 marks

## Mark scheme (4 marks)

1. DNA replication produces two identical DNA double helices from one parental molecule (semi-conservative replication), so each chromatid of a replicated chromosome carries a complete copy of that DNA sequence.
2. Each replicated chromosome consists of two sister chromatids joined at the centromere, meaning the entire genome is duplicated before cell division begins.
3. During mitosis, sister chromatids are separated at anaphase when cohesin is cleaved, so one chromatid moves to each pole, ensuring each daughter cell receives one copy of every chromosome.
4. Because both daughter cells each receive one sister chromatid from every replicated chromosome, the genome in each daughter cell is identical to the original parent cell genome.

## Key terms

- [genome](https://www.gradenine.co.uk/glossary/genome)

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-dna-replication-during-s-58678d94) · Published by Druglandscape Ltd.