IB Biology HL 1.2.6 DNA Double Helix Question Bank
Practise IB Biology HL 1.2.6 by interpreting diffraction evidence and analysing antiparallel strands, backbone links and base pairs.
- Syllabus
- First assessment 2025
- Course
- Biology HL
- Level
- HL
Practise IB Biology HL 1.2.6 by interpreting diffraction evidence and analysing antiparallel strands, backbone links and base pairs.
Draw a labelled diagram of the molecular structure of DNA, comprising of four nucleotides.
deoxyribose, phosphate and base / named base properly labelled and linked;
all four bases labelled as Adenine, Thymine, Cytosine, Guanine;
sugar labelled and shown as a pentagon;
covalent / phosphodiester bonds correctly labelled;
complementary base pairing between A-T and C-G;
H-bonds correctly labelled;
correctly shows two antiparallel sugar-phosphate strands / backbones with linkages between phosphates and sugars connected through bases.

Full names required for any base drawn. Do not award marks for letters alone.
Phosphate and simple names such as sugar and base are acceptable labels. They must be given at least once.
Award [2 max] if no complementary double stranded molecule.