Describe how a gene in the nucleus controls the production of a specific protein at a ribosome.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A gene is a stretch of DNA that codes for a specific protein. The sequence of bases in the gene determines the sequence of amino acids in the protein. In the nucleus the gene is transcribed to produce an mRNA copy. The mRNA exits the nucleus and travels to a ribosome in the cytoplasm. The ribosome reads the mRNA sequence and assembles a chain of amino acids, forming the specific protein.
Examiner tips
- Use the word ‘transcribed’ for the DNA to mRNA step
- Mention the ribosome is in the cytoplasm
- Show the link between base sequence and amino acid sequence
- Keep the answer concise and use correct terminology
Common mistakes
- Confusing transcription with translation
- Forgetting that the ribosome is in the cytoplasm
- Using ‘protein’ instead of ‘mRNA’ for the intermediate
Mark scheme (4 marks)
- A gene is a length of DNA that codes for a specific protein / the sequence of bases in a gene determines the sequence of amino acids in a protein.
- The gene is used to make an mRNA copy in the nucleus.
- The mRNA leaves the nucleus and travels to a ribosome in the cytoplasm.
- The ribosome uses the sequence of bases on the mRNA to assemble a chain of amino acids, forming the specific protein.
Key terms in this question
Related
- All Cambridge International IGCSE Biology (0610) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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