# Explain how errors in DNA replication can lead to frameshift mutations and outline why frameshift mutations are often more damaging to protein function than missense mutations.

> IB DP Biology Higher Level (2023 syllabus) — D1.3 Mutations and gene editing (HL only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Frameshift mutations arise when nucleotide insertions or deletions (indels) that are not multiples of three occur during replication, shifting the reading frame of codons downstream of the mutation.
2. Replication errors such as slippage of DNA polymerase on repetitive sequences (e.g. microsatellites) can cause the polymerase to skip or duplicate nucleotides, introducing these indels.
3. A frameshift alters every codon from the point of the mutation to the stop codon, producing a completely different (and usually non-functional) amino acid sequence in that region.
4. A missense mutation changes only a single amino acid, so the remainder of the primary sequence is unaffected and the protein may retain partial or full function; frameshifts are therefore typically far more disruptive to protein structure and function.

## Key terms

- [frameshift mutation](https://www.gradenine.co.uk/glossary/frameshift-mutation)
- [missense mutation](https://www.gradenine.co.uk/glossary/missense-mutation)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](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/explain-how-errors-in-dna-replication-71192010) · Published by Druglandscape Ltd.