Question 23M.3.SL.TZ1.9
| Date | May 2023 | Marks available | [Maximum mark: 5] | Reference code | 23M.3.SL.TZ1.9 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Describe, Outline, Suggest | Question number | 9 | Adapted from | N/A |
When apples are damaged or cut, exposure to oxygen causes the enzyme polyphenol oxidase (PPO) to oxidize polyphenols in the apple, a reaction that leads to the flesh becoming brown. Scientists have developed transgenic apples in which browning does not occur.
Suggest a reason for browning not occurring in the transgenic apple.
[1]
the enzyme/PPO was absent/deactivated/inhibited/replaced;
Usually a correct answer was seen.
A marker gene in transgenic apples produces a protein called NPTII. Outline the role of marker genes.
[1]
they allow scientists to know that the (trans)gene has been added (correctly/successfully);
OWTTE
No correct answers seen.
Describe how electroporation can be used to produce transgenic plants.
[2]
- cell wall removed/protoplast used;
- electric field applied;
- makes pores in cell membrane to allow genes to enter cells;
No correct answers seen and the process of electroporation was unknown.
Herbicide-resistant GM crops have been blamed for causing several environmental problems in the last few decades. Some weeds now have tolerance to herbicides. Suggest how this might have occurred.
[1]
gene flow/cross pollination/hybridisation;
No correct answers seen.