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Date May 2018 Marks available 3 Reference code 18M.3.HL.TZ2.12
Level Higher level Paper Paper 3 Time zone Time zone 2
Command term Outline Question number 12 Adapted from N/A

Question

A protein expressed by the gene carotene desaturase (CTP1) was introduced into Golden rice (Oryza sativa) through genetic engineering. Bioinformatics were used to determine if the protein sequence matched any allergenic proteins (proteins that trigger an allergic reaction). The table shows the results from the alignment of the CTP1 protein with proteins from moth, soybean and dust mite that are known to be allergenic.

State a bioinformatic search tool that could be used to perform the alignment.

[1]
a.i.

Outline how the similar protein sequences were found.

[1]
a.ii.

Regulations say that a protein is considered allergenic and unsafe for human consumption if at least 80 amino acids are aligned and there is greater than 35 % identity with any known allergen. Analyse the data provided to consider whether CTP1 is safe for human consumption.

[3]
b.

Genes such as the one coding for CTP1 can be located by searching for open reading frames. Outline how open reading frames are identified.

[3]
c.

Physical and chemical methods can be used to genetically modify crop plants by inserting new genes. List a physical and a chemical method that could have been used to introduce the gene coding for CTP1 into the rice plants.

 

[2]
d.

Markscheme

BLASTp
OR
ClustalW
OR
FASTA3

a.i.

database/named database searched to compare newly identified sequences with sequences of known function in other organisms

a.ii.

a. dust mite protein has 45% identity with CTP1 which could be unsafe 

b. only 36 aligned amino acids of dust mite protein which is less than the 80 danger limit 

c. both moth and soybean protein have less than 35% identity so are considered safe 

d. both moth and soybean protein have more than 80 amino acids aligned so could be unsafe 

e. CTP1 is not an allergen as it does not fit the criteria for any allergen
OR
CTP1 from the three organisms is not over the safety limit in the two categories so are considered safe

b.

a. a DNA sequence with a promoter, a start and a stop codon 

b. start codon is ATG 

c. stop codon is TAA/TAG/TGA 

d. nucleotide sequence with a considerable length 

e. named bioinformatics software
OR
ORF finder

Allow other verifiable answer.

c.

a. physical:
electroporation
OR
microinjection
OR
biolistics «gunshot» 

Allow other verifiable answer.

b. chemical:
calcium chloride
OR
liposomes

Allow other verifiable answer.

d.

Examiners report

[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.
[N/A]
c.
[N/A]
d.

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)
Option B: Biotechnology and bioinformatics

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