# Explain how molecular sequence data, such as base sequences of DNA or amino acid sequences of proteins, can be used to determine the evolutionary relationships between species.

> IB DP Biology Standard Level (2023 syllabus) — A3.2 Classification and cladistics · Explain · 4 marks

## Mark scheme (4 marks)

1. Species that share a more recent common ancestor will have more similar molecular sequences (DNA or protein).
2. Mutations accumulate over time in molecular sequences at an approximately constant rate, so the number of differences between sequences reflects the time since divergence.
3. Sequence data can be used to construct cladograms / phylogenetic trees that show branching patterns of evolutionary divergence.
4. Molecular data provides an objective, independently verifiable source of evidence that can support or revise classifications based on morphology alone.

## Key terms

- [molecular sequence data](https://www.gradenine.co.uk/glossary/molecular-sequence-data)
- [amino acid sequence](https://www.gradenine.co.uk/glossary/amino-acid-sequence)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-molecular-sequence-data-such-393ec436) · Published by Druglandscape Ltd.