D1.2.7—Complementary base pairing
Complementary base pairing between mRNA codons and tRNA anticodons ensures that each codon recruits the correct amino acid carrier during translation.
- Syllabus
- First assessment 2025
- Objective
- D1.2.7
- Level
- SL
Exam analysis
Chance of appearing3%of analysed past papers
Latest appearanceNovember 2022
Most common paperPaper1
Typical marks1–3
Common command terms
- Outline
- Explain
Scoring notes
- Common mistake
- Using DNA base-pairing letters instead of RNA uracil when writing anticodons.
Recent exam appearances
November 2022Paper1 ["SL"] · TZ010[ 1 ]D1.2.7—Complementary base pairing
May 2019Paper1 ["SL"] · TZ29[ 1 ]D1.2.7—Complementary base pairing
May 2017Paper2 ["SL"] · TZ15(a)[ 3 ]D1.2.7—Complementary base pairing
May 2012Paper1 ["SL"] · TZ27[ 1 ]D1.2.7—Complementary base pairing
Practice this objective
Coverage 2012–2022 · Updated 16 Jul 2026
Concept essentials
- mRNA codons pair with complementary tRNA anticodons.
- RNA base pairing uses A with U and C with G.
- Correct amino acid addition depends on both anticodon pairing and tRNA charging.
- The anticodon identifies the codon read at the ribosome, not the original DNA triplet directly.