Question 19N.2.SL.TZ0.a
| Date | November 2019 | Marks available | [Maximum mark: 4] | Reference code | 19N.2.SL.TZ0.a |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Draw | Question number | a | Adapted from | N/A |
Draw the structure of a section of DNA showing all possible bases.
[4]
a. sugar, phosphate and base linked correctly to form at least one nucleotide ✔ For mpa, ignore labelling of the subunits of the nucleotide. Carbon atoms in deoxyribose do not have to be numbered but the phosphate should be linked to C5 and the base to C1. Shapes other than circles and rectangles could be used for the phosphate and base.
b. deoxyribose, phosphate and base/named base labelled at least once ✔
c. adenine paired with thymine and cytosine paired with guanine ✔ For mpc, full names of all four bases are required, but not relative sizes of the purine and pyrimidine bases.
d. two antiparallel chains of nucleotides linked by hydrogen bonds with all sugar-phosphate bonds in correct position ✔ For mpd, a bond should connect the C3 of deoxyribose on one nucleotide to the phosphate on the adjacent nucleotide. Two nucleotides in each strand is sufficient.
