# A scientist studies DNA replication in human liver cells. Explain how a single molecule of DNA produces two identical copies of itself during DNA replication.

> WJEC A-Level Biology (Wales) — 1.5 Nucleic acids and DNA replication · Explain · 5 marks

> Human liver cells must replicate their DNA during the cell cycle before cell division can occur. DNA replication takes place in the nucleus and ensures that each new daughter cell receives a full set of genetic information.

## Mark scheme (5 marks)

1. DNA double helix unwinds / two strands separate
2. Each original strand acts as a template for a new strand
3. Complementary base pairing occurs — new bases pair with exposed bases on the template strand
4. Two new identical double-stranded DNA molecules are formed
5. Each new DNA molecule contains one original strand and one new strand (semi-conservative replication)

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-scientist-studies-dna-replication-in-e93a0297) · Published by Druglandscape Ltd.