Question 21M.2.SL.TZ1.b
| Date | May 2021 | Marks available | [Maximum mark: 2] | Reference code | 21M.2.SL.TZ1.b |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Compare and contrast | Question number | b | Adapted from | N/A |
Antiretroviral drugs are used to treat Human Immunodeficiency Virus (HIV) infections. Zidovudine (ZDV) and nevirapine (NVP) are examples of antiretroviral drugs. There are concerns that these drugs may be toxic to body cells in mitosis. In a study using Allium cepa, root tips were exposed to the drugs for 96 hours at a range of concentrations. The control treatment was a drug concentration of 0μmol. In the graph, root lengths after the 96-hour treatment period are expressed as a percentage of the length of the control.
[Source: Onwuamah CK, Ekama SO, Audu RA, Ezechi OC, Poirier MC, Odeigah PGC (2014) Exposure of Allium cepa Root Cells to Zidovudine or Nevirapine Induces Cytogenotoxic Changes. PLOS ONE 9(3): e90296. https://doi.org/10.1371/journal.pone.0090296 (CC0 1.0 - https://creativecommons.org/publicdomain/zero/1.0/).]
Compare and contrast the effect of ZDV and NVP on the growth of Allium roots.
[2]
Similarities:
a. reduce root length (compared to the control) ✔
b. (ZDV and NVP) have greatest change (in growth) at lowest concentrations (of ZDV and NVP) ✔
c. same effect at 200 μmol ✔
d. above/at about 400 μmol effect levels off ✔
Differences:
e. the change/differences become significant after 200 μmol ✔
f. ZDV has a (slightly) larger effect / NVP has a (slightly) smaller effect / WTTE
OR
above 400 μmol effect of ZDV remains higher / NVP remains lower ✔
Answer must contain one similarity and one difference.
Credit may be given for numeric differences when accurately stated.
There was a tendency to describe data rather than interpreting it. Instead of writing that root length was reduced, students simply compared numbers. Commonly either a comparison or a contrast was missing.
