| Date | November 2011 | Marks available | 1 | Reference code | 11N.3.hl.TZ0.B6 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Describe | Question number | B6 | Adapted from | N/A |
Question
DNA is the genetic material that individuals inherit from their parents. Genetic information is stored in chromosomes which are very long strands of DNA.
Describe the structure of a nucleotide of DNA.
Outline how nucleotides are linked together to form polynucleotides.
Markscheme
phosphate group and pentose/deoxyribose (sugar) and organic/nitrogenous base;
Accept suitable diagram.
No mark for just sugar or just base.
condensation reaction / covalent bond between phosphate on one nucleotide and pentose sugar on next;
Accept suitable diagram.
Penalize just sugar only once.
Examiners report
Many scored the mark for the structure of a nucleotide of DNA - usually the ones who did not score the mark failed to mention the base being organic or nitrogenous or the sugar being pentose or deoxyribose.
About half the candidates incorrectly stated hydrogen bonding in relation to how nucleotides are linked together.
