# Explain how the sequence of bases in a gene determines the sequence of amino acids in a protein.

> Pearson Edexcel A-Level Biology A (9BI0) — 1.4 DNA, RNA and protein synthesis · Explain · 5 marks

> Proteins are made up of long chains of amino acids. The order of amino acids determines the shape and function of each protein. The instructions for making proteins are stored in DNA inside the nucleus of a cell.

## Mark scheme (5 marks)

1. The gene (section of DNA) contains a specific sequence of bases / the base sequence acts as a code
2. The sequence of bases on DNA is used to make a complementary strand of mRNA (transcription)
3. The mRNA moves out of the nucleus to a ribosome
4. Each sequence of three bases (triplet / codon) on the mRNA codes for a specific amino acid
5. Amino acids are joined together in a specific order (translation) to form the protein / polypeptide chain

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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-sequence-of-bases-9d5cc59a) · Published by Druglandscape Ltd.