# A student states: 'DNA is found in the nucleus of eukaryotic cells. Before a cell can divide by mitosis, the DNA must be copied so that each daughter cell receives identical genetic information.' Explain why it is important that both daughter cells receive an identical copy of the DNA, and describe the role of complementary base pairing in producing those identical copies.

> Eduqas A-Level Biology — 1.5 Nucleic acids and DNA replication · Explain · 5 marks

> DNA is a polymer made of two strands twisted around each other to form a double helix. Each strand is made up of nucleotides, and the bases on one strand are complementary to the bases on the opposite strand.

## Mark scheme (5 marks)

1. Each daughter cell must contain the same genetic information / genes as the parent cell so that it can produce the same proteins / function correctly
2. The two strands of the double helix separate / unwind
3. Each original strand acts as a template for a new complementary strand
4. Complementary base pairing ensures that the correct base is added to each position on the new strand
5. The result is two identical DNA molecules, each containing one original strand and one new strand

## Key terms

- [DNA](https://www.gradenine.co.uk/glossary/dna)
- [complementary base pairing](https://www.gradenine.co.uk/glossary/complementary-base-pairing)
- [daughter cells](https://www.gradenine.co.uk/glossary/daughter-cells)
- [genetic information](https://www.gradenine.co.uk/glossary/genetic-information)

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-states-dna-is-found-4732ec72) · Published by Druglandscape Ltd.