2026 SACE Biology exam: What to learn from last year's mistakes

Exam: Friday 6 November 2026, 9.00 am. South Australia local time.

I've gone through last year's examiner advice. Q21 had the lowest mean in Section 2; Q16 had the highest. Even in the strongest question, students lost marks by using the codon table incorrectly or stopping before explaining the effect on the protein.

1. Q16(f) and (g): Read the mRNA, then explain the consequence

Where students went wrong

Some converted mRNA back into a complementary DNA template before using the codon table. Others didn't connect an unchanged amino acid to an unchanged protein sequence.

What they should have done

Follow the sequence type and direction given. Use the mRNA codons directly with an mRNA codon table. If a substitution leaves the encoded amino acid unchanged, explain why that particular change does not alter the protein's amino-acid sequence.

For revision, label every sequence DNA template, coding DNA or mRNA before translating. That one line can prevent a whole chain of wrong answers.

2. Q17(e)(ii): Answer for the cell in the figure

Where students went wrong

Most weaker responses gave generic facts about meiosis instead of using Figure 6 and its key.

What they should have done

Trace the chromosomes and labels shown for cell B. Describe the resulting cells using that information. Don't substitute the familiar human chromosome numbers into a different organism's example.

Try explaining what each symbol in the key represents before writing. If the figure disappeared and your answer would be exactly the same, check whether you've used the evidence requested.

3. Q19(a): Join iodine to body temperature

Where students went wrong

Answers missed links between iodine, thyroxine, metabolic rate and heat production.

What they should have done

Explain the causal sequence rather than listing four related terms. Iodine is needed to make thyroid hormones; those hormones influence metabolic activity, which affects heat production and therefore temperature regulation.

In a mechanism answer, each sentence should explain why the next step follows. Use the direction of change supplied in the question rather than writing a memorised paragraph that could describe either an increase or a decrease.

4. Q21(b): DNA sequences can distinguish changes that proteins hide

Where students went wrong

Some discussed DNA–DNA hybridisation instead of answering the sequencing comparison.

What they should have done

Explain genetic-code degeneracy: different codons can specify the same amino acid. Protein sequencing therefore doesn't uniquely reveal the underlying nucleotide sequence, whereas sequencing the gene examines that sequence directly.

As a check, choose two codons for one amino acid from your table. You now have a concrete example of why identical amino-acid information doesn't require identical DNA information.

These are selected lessons from the 2025 Biology examiner advice, not predictions. Use the official Biology resources and check the 2026 timetable.

Sorry guys, shameless plug, I gotta do this. I'm the founder of ATARMAXXING, so take a look at the SACE Biology practice exams with worked answers if you want more practice. You can preview the Biology pack before buying. Practise applying the theory to a new figure, then check every link in your explanation.

Discuss this SACE Biology exam breakdown on the subject board.