# Explain how alternative splicing of a pre-mRNA transcript enables a single gene to produce more than one functional protein.

> IB DP Biology Higher Level (2023 syllabus) — D2.2 Gene expression (HL only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Pre-mRNA contains both exons (coding sequences) and introns (non-coding sequences) that must be processed before translation.
2. During RNA processing, different combinations of exons can be retained (and/or different exons excluded) to produce distinct mature mRNA molecules from the same pre-mRNA.
3. Each distinct mature mRNA is translated to produce a polypeptide with a different amino acid sequence / primary structure.
4. Because protein function depends on its three-dimensional structure (which arises from its amino acid sequence), each polypeptide isoform can have a distinct function.

## Key terms

- [alternative splicing](https://www.gradenine.co.uk/glossary/alternative-splicing)
- [pre-mRNA](https://www.gradenine.co.uk/glossary/pre-mrna)

## 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-alternative-splicing-of-a-183610e9) · Published by Druglandscape Ltd.