D1.2.8—Genetic code features
The genetic code uses mRNA triplets to specify amino acids, start and stop signals, while degeneracy reduces some mutation effects.
- Syllabus
- First assessment 2025
- Objective
- D1.2.8
- Level
- SL
Exam analysis
Chance of appearing6%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1
Typical marks1
Common command terms
- Identify
- Outline
- Suggest
- Describe
Scoring notes
- Common mistake
- Counting amino acids as if one base rather than three bases codes for each residue.
Recent exam appearances
November 2025Paper1A ["SL"] · TZ16[ 1 ]D1.2.8—Genetic code features
May 2024Paper1 ["SL"] · TZ210[ 1 ]D1.2.8—Genetic code features
May 2022Paper1 ["SL"] · TZ110[ 1 ]D1.2.8—Genetic code features
November 2019Paper2 ["SL"] · TZ02(c)[ 1 ]D1.2.8—Genetic code features
November 2019Paper2 ["SL"] · TZ02(a)[ 1 ]D1.2.8—Genetic code features
Practice this objective
Coverage 2015–2025 · Updated 16 Jul 2026
Concept essentials
- A codon is a triplet of bases on mRNA.
- Most codons specify one amino acid in a polypeptide.
- Start and stop codons define where translation begins and ends.
- Degeneracy means multiple codons can code for the same amino acid.