A-LevelBiologyGenetic technology9700/41 · May/June 2017 · Q314 Marks
Oil seed rape (canola), Brassica napus, has been genetically modified to be resistant to herbicides containing glufosinate ammonium. The genetically modified (GM) oil seed rape contains the bar gene, obtained from a soil bacterium. This gene codes for an enzyme that converts glufosinate ammonium into a non-toxic compound.
- (a)Outline the advantages to farmers of growing glufosinate-resistant oil seed rape.[2]
- (b)(i)Outline the structure of a plasmid.[2]
- (b)(ii)Explain how the properties of plasmids make them suitable for use during genetic modification programmes.[3]
- (b)(iii)Describe the role of a promoter in gene expression.[2]
- (c)(i)Predict the diploid number of chromosomes in a hybrid between oil seed rape and wild radish.[1]
- (c)(ii)Suggest how the researchers could have determined whether or not the bar gene was present in the plants.[1]
- (c)(iii)Many varieties of GM oil seed rape are male sterile, meaning that they do not produce pollen. With reference to Table 3.1, suggest the advantages to the environment of growing male sterile varieties of GM oil seed rape, rather than GM varieties that produce pollen.[3]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- max 2 of:
- 1 can, kill / control, weeds ; R kill, insects / pests
- 2 reduce competition / increase yield (of rape);
- 3 AVP; e.g. manual weeding / hoeing, difficult / expensive ref. to glufosinate converted to non-toxic compound
- circle of/ circular, DNA ; I loop R single-stranded
- small/supplementary ;
- max 3 of:
- 1 small so can be taken up by, cells / bacteria;
- 2 replicate, independently / fast; A have ori/ origin of replication / high copy number
- 3 (DNA) has restriction site(s) / can be cut by restriction enzymes ; A have polylinker
- 4 have, marker genes / genes for resistance (for screening);
- 5 AVP; e.g. circular so, increased stability / reduced host cell degradation
- max 2 of:
- 1 RNA polymerase binds ;
- 2 so, transcription / mRNA synthesis, begins / occurs / allowed ;
- 3 AVP; e.g. correct/template, strand is transcribed ref. to tissue-specific / inducible, expression
- [1] 28;
- max 1 of:
- spray with herbicide and, those that die did not have the bar gene / those that survive did have the bar gene;
- add gene for fluorescence with bar gene and test plants under UV/use PCR with primer complementary to bar gene / use (gene) probe (on Southern blot) of electrophoresis gel ;
- max 3 of:
- advantage of male sterile GM variety
- 1 avoid transferring, bar/ resistance, gene to wild, radish / relations; ora
- 2 avoid superweeds; ora
- 3 avoid type 2 hybrids ; ora
- disadvantage of type 2 hybrids (from GM variety that produces pollen)
- 4 taller (than wild radish); A very tall / 88 cm / 95 cm
- 5 produce, more / many, seeds (than wild radish); A 3958/443 more
- 6 may (out)compete, wild radish / crops ;
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