| Date | November 2010 | Marks available | 5 | Reference code | 10N.3.hl.TZ0.B4 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Describe and Explain | Question number | B4 | Adapted from | N/A |
Question
Nucleic acids are natural polymers with exceptionally large relative molecular masses, made up of nucleotides. All cells in the human body, with the exception of red blood cells, contain deoxyribonucleic acid (DNA).
James Watson, Francis Crick and Maurice Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine “for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living material”.
(i) Explain how the two helices are linked in the structure of DNA.
(ii) Describe the role of DNA in the storage of genetic information. The details of protein synthesis are not required.
Markscheme
(i) bases;
held together by hydrogen bonds;
(ii) coded information lies in sequence of bases;
each sequence of three bases represents one amino acid/triplet code;
allows for up to 64 permutations/codons;
represents 20 naturally occurring amino acids;
human genome / complete sequence of bases in human DNA;
Examiners report
Usually candidates had no problem scoring both marks for (a) (i). In (ii) however, many answers were too broad in scope dealing with transcription and translation, rather than concentrating on how the genetic information is stored. Candidates clearly did not interpret what was being asked for explicitly in the question.
