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Date May 2019 Marks available 3 Reference code 19M.3.SL.TZ1.9
Level Standard level Paper Paper 3 Time zone Time zone 1
Command term Outline Question number 9 Adapted from N/A

Question

Some bacterial genes are used as marker genes. Outline the use of marker genes in genetic modification.

[3]
a.

Outline the process of producing bulk quantities of hepatitis B vaccine in tobacco plants.

[4]
b.

Markscheme

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 ✔

a.

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 ✔

b.

Examiners report

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.

a.

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.

b.

Syllabus sections

Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics) » B.2 Biotechnology in agriculture
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Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics)
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