Explain how the sequence of bases in a gene determines the structure of a protein.

Eduqas GCSE Biology — 7.1 The genome and gene expression · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

A gene is a section of DNA that contains a sequence of bases.
The sequence of bases is read in groups of three (codons) during transcription and translation, and each codon specifies a particular amino acid.
The amino acids are joined together by peptide bonds to form a polypeptide chain, i.e. a protein.
The order of amino acids determines the protein’s primary structure, which folds into a specific three‑dimensional shape that gives the protein its function.

Examiner tips

Use the exact terms: gene, DNA, bases, codon, amino acid, polypeptide, protein, structure, function.
Show the flow from DNA → RNA → amino acids → protein structure.
Keep each point short and directly linked to the marks.
Mention that the codon sequence determines the amino acid sequence.

Common mistakes

Confusing DNA with RNA or not mentioning codons.
Saying the protein’s shape is random instead of determined by amino acid sequence.
Using vague words like ‘sequence’ without specifying amino acids or codons.

Mark scheme (4 marks)

A gene is a section of DNA that contains a sequence of bases
The sequence of bases codes for the sequence of amino acids in a protein
Amino acids are joined together to form a polypeptide / protein
The sequence of amino acids determines the shape / structure of the protein, which determines its function

Key terms in this question

gene · protein