Question 21M.2.HL.TZ1.8b
| Date | May 2021 | Marks available | [Maximum mark: 4] | Reference code | 21M.2.HL.TZ1.8b |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Outline | Question number | b | Adapted from | N/A |
Outline the role of DNA polymerase III in DNA replication.
[4]
a. binds to template strand adjacent to a primer/at the primer ✔
b. adds nucleotides to template strand/to single stranded DNA ✔
c. using complementary base pairing ✔
d. links nucleotides with sugar-phosphate/phosphodiester bonds ✔
e. adds nucleotides/builds new strand in 5' 3' direction ✔
f. lagging strand is built in short segments/Okazaki fragments/synthesis is discontinuous ✔
Accept A to T and G to C instead of ‘complementary’ in mpc.
For mpb it must be clear that nucleotides, not bases, are added to an existing strand of DNA. Do not accept ‘to replication fork’ for this.
For the well-prepared candidate, this posed no problems and the four marks were easily earned. At the other end of the performance range almost all candidates mentioned Okazaki fragments — a benefit of giving something a distinctive name.
