HSC Biology free practice questions with answers
Read question 1 and its full worked answer from paper 1 of our 20-paper HSC Biology set, then download the 4-page PDF. These are original practice questions, not official past papers. Page updated 3 November 2026.
A mutation replaces the base at position 10 (A) with T in the coding sequence
5'–ATGGATGAGAAATACTAA–3'. The original polypeptide has 5 amino acids. Use the genetic code on the data sheet. Which term best describes this mutation and its effect?
A A nonsense mutation: a premature stop codon shortens the polypeptide
B A frameshift mutation: the reading frame changes from the deletion onwards
C A silent mutation: the polypeptide is unchanged
D A missense mutation: one amino acid is changed
Correct answer: A — A nonsense mutation: a premature stop codon shortens the polypeptide
- Translate the original and the mutated sequence codon by codon.
- Original: Met–Asp–Glu–Lys–Tyr. Mutated: Met–Asp–Glu.
- Compare: the new codon is a stop codon, so translation ends early.
- Why the other options are wrong:
- B (A frameshift mutation: the reading frame changes from the deletion onwards): this does not fit the comparison of the two polypeptides
- C (A silent mutation: the polypeptide is unchanged): this does not fit the comparison of the two polypeptides
- D (A missense mutation: one amino acid is changed): this does not fit the comparison of the two polypeptides
Silent = same amino acid; missense = different amino acid; nonsense = premature stop; insertions/deletions that are not multiples of 3 cause frameshifts that change all downstream amino acids.
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Questions about this sample
What is in the HSC Biology free sample?
The first 3 questions from paper 1 of the set, in the real exam layout, followed by the step-by-step worked answers. It is a 4-page PDF; this page shows question 1 with its answer.
How many full HSC Biology papers are there?
20 original papers for Year 12 students preparing for the NSW HSC. Each is a full practice examination with Section I 20 multiple-choice, Section II 80 marks, 100 marks in all, 3 hours working time plus 10 minutes reading time, with a worked solution for every question. Papers start at A$15.99 and download instantly as a PDF.
Are these official past papers?
No. The sample is taken from our own original practice paper and is not an official past paper or affiliated with any exam authority.