Question 19M.3.SL.TZ1.9
| Date | May 2019 | Marks available | [Maximum mark: 7] | Reference code | 19M.3.SL.TZ1.9 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Outline | Question number | 9 | Adapted from | N/A |
Some bacterial genes are used as marker genes. Outline the use of marker genes in genetic modification.
[3]
a. named example of a marker gene, eg: ampicillin resistance ✔
b. target gene and marker gene combined «in the same construct» ✔
c. taken up by host ✔
d. evidence of the marker gene measurable ✔
e. indicates successful gene modification/incorporation ✔
Marker genes were often described as desired or target genes in gene transfer and their role was not understood. No reference to antibiotic resistance genes was seen.
Outline the process of producing bulk quantities of hepatitis B vaccine in tobacco plants.
[4]
a. hepatitis B gene coding for an antigen ✔
b. fused with a tobacco mosaic virus/capsid gene ✔
c. tobacco plant is infected with the «recombinant» virus ✔
d. hepatitis B antigens are extracted from the plants ✔
e. antigens are purified to produce vaccine ✔
f. «antigens in» the vaccine stimulates antibody production ✔
Candidates did not understand this question and if answered at all, described infecting tobacco with the hepatitis B virus, then extracting antibodies. Credit was given for purification of the antigens, which was often the only mark gained.