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AS & A Level · AS/A Level

Biology

DNA and gene expression

Name: ____________________Date: October 10, 2026
  1. 1.

    Explain the complementary base pairing that maintains information during DNA replication.

    [3 marks] · no calculator
  2. 2.

    Distinguish the role of mRNA from that of tRNA in translation.

    [3 marks] · no calculator
  3. 3.

    A coding DNA strand is 5'-ATG GAA TTT TGA-3'. Given AUG=Met, GAA=Glu, UUU=Phe and UGA=stop, write the mRNA and resulting peptide, assuming initiation at the first AUG.

    [3 marks] · no calculator
  4. 4.

    Explain why deletion of one nucleotide early in a coding region can have a larger effect than substitution of one nucleotide.

    [3 marks] · no calculator
  5. 5.

    Cells with identical DNA can make different proteins. Explain this through transcriptional regulation and mRNA processing rather than proposing different genetic codes.

    [4 marks] · no calculator
  6. 6.

    A gene variant is associated with a disease in a case-control study. Evaluate why association alone does not prove that its encoded protein causes the disease, and propose stronger evidence.

    [4 marks] · no calculator

Original, unofficial practice questions from SubjectScout — not official past-paper questions.

Marking points are indicative, not an official mark scheme. Accept equivalent valid methods and supported interpretations that address the task; award each mark once without requiring the model wording.