Question 23M.3.HL.TZ1.10
| Date | May 2023 | Marks available | [Maximum mark: 4] | Reference code | 23M.3.HL.TZ1.10 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Describe, Outline, Suggest | Question number | 10 | 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;
Many candidates could correctly suggest a reason the transgenic apple did not turn brown.
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
Many also correctly could outline the role of marker genes.
Describe how calcium chloride can be used in genetic modification.
[2]
- host cells are in solution with calcium chloride at low/cold temperatures;
- the temperature of the solution is quickly raised/heat shock;
- chemical method to enhance plasmid/DNA uptake by (bacteria) cells
OR
induces competence for transformation;
OWTTE
Very few candidates understood the use of calcium chloride in genetic modification.
