A scientist studied a section of DNA and found that it contained 120 bases. The scientist then observed the process of transcription and translation to produce a protein. Describe the roles of messenger RNA (mRNA) and transfer RNA (tRNA) in the synthesis of a protein.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A section of DNA contains 120 bases. The scientist observed transcription and translation occurring in a cell to produce a protein from this DNA.
Model answer (5 marks)
mRNA is produced in the nucleus during transcription and carries the genetic code from the nucleus to the ribosome.
tRNA carries specific amino acids to the ribosome and has an anticodon that pairs with the complementary codon on the mRNA.
The amino acids brought by tRNA are joined together in the order dictated by the mRNA sequence to form a protein (polypeptide) at the ribosome.
tRNA carries specific amino acids to the ribosome and has an anticodon that pairs with the complementary codon on the mRNA.
The amino acids brought by tRNA are joined together in the order dictated by the mRNA sequence to form a protein (polypeptide) at the ribosome.
Examiner tips
- Use the word ‘produced’ for mRNA and ‘carries’ for both mRNA and tRNA. Mention the nucleus for transcription and the ribosome for translation. State the anticodon–codon pairing for tRNA. Show that amino acids are joined in the mRNA‑determined order.
- common_mistakes
- :
- Confusing the location of transcription (nucleus) with translation (cytoplasm). Forgetting to mention the anticodon on tRNA. Saying tRNA ‘carries’ the protein instead of the amino acid.
Mark scheme (5 marks)
- mRNA is produced/made in the nucleus (during transcription)
- mRNA carries the genetic code / base sequence from the nucleus to the ribosome
- tRNA carries / brings specific amino acids to the ribosome
- tRNA has an anticodon that pairs / matches with the complementary codon on the mRNA
- amino acids are joined together (in the order determined by the mRNA sequence) to form a protein / polypeptide (at the ribosome)
Key terms in this question
messenger RNA (mRNA) · transfer RNA (tRNA) · transcription · translation
Related
- All Edexcel A-Level Biology A: Salters-Nuffield (9BN0) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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