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The genetic code and protein synthesisEdexcel International A Level Biology: Flashcards

What these 12 flashcards ask

  • What is a gene?
  • What does it mean that the code is a triplet code?
  • What does non-overlapping mean?
  • What does degenerate mean?
  • Why is the code degenerate?
  • What is the start codon?
  • Name the three stop codons.
  • Which DNA strand is the template (antisense) strand?
  • What does RNA polymerase do in transcription?
  • What is an anticodon?
  • What forms between amino acids at the ribosome?
  • A polypeptide has 100 amino acids. How many bases does the mRNA read by the ribosome contain, including a stop codon?

Exam questions on The genetic code and protein synthesis

  1. The template (antisense) strand of a short section of a gene has the base sequence TACGGATTC. The section is transcribed into messenger RNA.
    The codon CCU in the mRNA codes for the amino acid proline. A mutation in the gene changes this codon to CCC, which also codes for proline. Explain why the polypeptide is unchanged.2 marks
  2. A ribosome is translating a short mRNA with the codon sequence AUG GCU UUC UAA. Transfer RNA molecules, each carrying a specific amino acid, deliver the amino acids to the ribosome.
    State the number of amino acids in the polypeptide made from this mRNA and explain your answer.2 marks
  3. A student is studying a bacterial gene whose polypeptide product has 150 amino acids, including the first, methionine. The student is also learning why the genetic code uses sequences of three bases.
    Calculate the minimum number of bases in the mRNA that is read by the ribosome to make this polypeptide. Explain your answer.3 marks
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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).