# Explain how the double helix structure of DNA enables the molecule to carry out both storage and transmission of genetic information.

> IB DP Biology Standard Level (2023 syllabus) — A1.2 Nucleic acids · Explain · 4 marks

## Mark scheme (4 marks)

1. The sequence of bases along the DNA strand encodes genetic information / acts as a genetic code.
2. Complementary base pairing (A–T and C–G) between the two strands means each strand can serve as a template for replication.
3. The two strands are held together by hydrogen bonds, which are weak enough to allow strand separation during replication or transcription.
4. The helical / double-stranded structure protects the base sequence from chemical damage / the sugar–phosphate backbone shields the bases on the outside, contributing to long-term stable storage of information.

## Key terms

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

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](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/explain-how-the-double-helix-structure-d88cfd62) · Published by Druglandscape Ltd.