Draw a labelled diagram of the structure of DNA, showing the arrangement of subunits.

Explain DNA replication.

correctly shows two antiparallel sugar-phosphate strands/backbones with linkages between phosphates and sugars connected through bases; (phosphate and simple names such as sugar and base are acceptable labels. They must be given at least once.)
correctly labeled phosphate and deoxyribose and base;
sugar linked to phosphates through correct pentagon corners/(5’–3’) linkages;
shows complementary base pairs of A-T/Adenine–Thymine and G-C/Guanine–Cytosine;
correctly indicates both covalent/phosphodiester and hydrogen bonds.

DNA replication is semi-conservative/daughter DNA molecule contains one parent strand and one new strand;
unwinding of double helix/separation of two strands by helicase;
separated (parent) strands become templates for new strands;
free/single nucleotides join (parent/template) strands through complementary base pairing;
DNA polymerase joins nucleotides in new strands;
Award [3] for the above points clearly shown in an annotated diagram.

The DNA diagram provided many ways to earn three marks. Complementary base pairing was an easy mark. Roughly 20% of the candidates failed to draw two strands. Most candidates did not show the anti-parallel nature of DNA and very few had the correct linkage at the pentagon corners.

It seems that every candidate knew about helicase and stated its function correctly. Thus, few zero answers appeared. DNA polymerase was also mentioned by many, but without the correct function. A few candidates confused replication with translation.