# Explain how the structure of a nucleotide monomer enables DNA to store genetic information and to be replicated accurately.

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

## Mark scheme (4 marks)

1. A nucleotide consists of a deoxyribose sugar, a phosphate group, and one of four nitrogenous bases (adenine, thymine, guanine, or cytosine).
2. The sequence of bases along a polynucleotide strand constitutes the genetic information, because the variable base sequence can encode instructions for protein synthesis.
3. Complementary base pairing (A–T and G–C via hydrogen bonds) between specific bases on opposite strands ensures each strand acts as a template, so the base sequence is copied accurately during replication.
4. The phosphate groups link adjacent deoxyribose sugars via phosphodiester bonds to form a stable sugar–phosphate backbone, maintaining the integrity of the polynucleotide strand so the base sequence is preserved between replications.

## Key terms

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

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-structure-of-a-b5ee591f) · Published by Druglandscape Ltd.