Identify the nitrogen source that results in the highest yield of citric acid.

State two uses for industrially produced citric acid.

Citric acid can be produced by either batch fermentation or continuous fermentation. Distinguish between these two methods.

Explain the significance of pathway engineering in the industrial use of microorganisms.

NH₄NO₃ / ammonium nitrate

food preservative, flavouring, (stabilizer) in alcohol production

Two answers for 1 mark.

Answer does not need to be in a table.

a. used to produce specific metabolites/chemicals/substances 

b. used to create/maintain optimum conditions for microorganism growth/maximum yield 

c. remove by-products / block competing pathways 

d. introduce new genes that increase efficiency/yield 

Calculate the diversity of site C. Working should be shown.

Site A has a higher Simpson’s reciprocal index than Site B showing that its diversity is higher.

Explain the reason that ecologists consider Site A to have a higher diversity than Site B, despite both sites having six different species present.

Discuss the advantages and disadvantages of in situ conservation methods.

a.

b. = 3.56 «allow 3.55»

a. the species in Site A are more evenly represented than site B 

b. site B has a large number of one species «but very few in the other 5» 

c. Simpson’s reciprocal index is a measure of species evenness as well as species richness

Advantages:
a. conservation in the natural habitat / ecosystem

b. the species will have all the resources that it is adapted to 

c. the species will continue to evolve in their environment / can maintain genetic diversity 

d. the species have more space so a bigger breeding populations can be kept 

e. it is cheaper to keep an organism in its natural habitat 

f. established food webs/ species interactions can be maintained

Disadvantages:

g. it is difficult to control illegal exploitation «eg poaching»/harder to monitor populations 

h. the area may need restoring / may be required for other purposes 

i. alien species are difficult to control 

j. species close to extinction are harder to conserve 

k. management/protection may represent a significant cost

Compare and contrast amylose with amylopectin.

Outline how the composition of starch differs in the Amflora potato compared to a normal potato.

State one industrial use of the Amflora potato.

Suggest one reason for concerns about growing GM crop varieties such as the Amflora potato on farms.

a. amylopectin is «more» branched/has 1,6 bonds
OR
amylopectin is less soluble in water ✔

b. both made up of glucose
OR
both are polysaccharides
OR
both are helical in shape
OR
both contain glycosidic bonds ✔

Accept converse statements

amflora contains «almost» no amylose/«almost» all amylopectin ✔

used in the paper/glue/textile/concrete industry ✔

a. encourages monocultures/reducing biodiversity ✔

b. may reduce natural resistance to pests/disease ✔

c. may cross-pollinate with non-GM crops ✔

d. disruption of practices of farming/agricultural land not being used for food production ✔

e. crop-to-crop gene flow ✔

Outline the trend in amount of salt in the soil over the study period.

State the name of the strategy that involves the use of organisms to remove toxic substances from a contaminated site.

Suggest how these genetically modified tomato plants could be useful to farmers.

Explain how a researcher could determine whether other species contained similar sequences to the AtNHX1 gene.

decrease with time «exponential»
OR
negative correlation

bioremediation

a.GM tomatoes could be used to grow a crop on salinized soil «that otherwise would kill the plants» 

b.tomato crop could be used to remove salt from the soil «if the harvested crop was removed»
OR
phytoremediation

a. use bioinformatics tools «to search for similar sequences» 

b. conduct database/Blast search 

c. evaluate sequence alignment

Discuss the hypothesis that the temperature at which starches form a gel depends on the degree of cross-linking of amylopectin.

State one advantage of potatoes with a high amylopectin content. 

The Amflora potato was approved for industrial applications in the European Union (EU) in 2010 and was withdrawn in January 2012 due to opposition. Discuss reasons for people supporting or opposing the introduction of the Amflora potato in the EU.

a. high amylopectin potatoes/low amylose need more heat to form gel «so hypothesis supported» ✓

b. «normal» potato and normal barley have similar amylose concentration but different gel formation temperatures «so hypothesis not supported» ✓

c. normal barley and high amylose barley have same gel formation temperature «so hypothesis not supported»

a. «high amylopectin potato starch is» used in paper production because it forms a clearer film «when forming a gel» 

b. «high amylopectin potato starch is» used in adhesive production as it forms a stickier paste 

c. «high amylopectin potato starch is» used in paper/adhesive production because there is less thickening of starch film/paste during storage compared to regular potato starch

supporting:

a. potatoes cheap to grow 

b. benefits farmers/local producers «so less pollution» 

c. reduces costs in «paper» industry eg: paper or adhesives

d. beneficial uses in industry

opposing:

e. perceived health risks/allergens 

f. may cross pollinate with existing species 

g. could be eaten accidentally

State the role of a vector in biotechnology.

Explain how the Hepatitis B vaccine is produced using TMV.

State the importance of marker genes in genetic modification.

carries/transfers genetic material into a cell

a. TMV contains RNA/is a retrovirus

b. gene of hepatitis B «virus» codes for antigen

    OR

    hepatitis B «virus» has a gene that induces an immune response

c. «antigen» fuses to capsid gene for TMV

d. two fused genes enter/infect the plant cells «using the virus as a vector»

e. mice fed with infected plants produce antibodies against hepatitis B

f. antibodies are extracted from mouse serum/blood

Allow other mammal

[Max 3 Marks]

marker genes show the «target» gene has been inserted

A. aceti is a Gram-negative bacterium. If a Gram staining procedure were carried out on a sample of A. aceti, predict the result that would be observed after decolourization.

A. aceti is a Gram-negative bacterium. If a Gram staining procedure were carried out on a sample of A. aceti, predict the result that would be observed after counterstaining.

List two abiotic variables that would need to be monitored during this fermentation process.

Describe one way in which microorganisms in this fermenter could be limited by their own activities.

Distinguish between batch fermentation and continuous fermentation.

Outline the concept of an emergent property.

the bacteria would be clear/colourless

would stain pink

Do not accept “violet” or “lilac”.

a. oxygen 

b. temperature 

c. pH levels 

d. CO₂

a. name of a factor 

b. description

eg
a. pH
b.lowered by «ethanoic» acid production.

eg
a. increase in temperature
b. due to metabolism.

eg
a. increased population size/reproduction
b. would limit resources.

eg
a. increased metabolic waste
b. reduce population.

Table format is not required.

a. emergent properties arise from the interaction of the elements of a system 

b. behaviours exhibited which are not shown by individuals 

c. quoroum sensing
OR
matrix production
OR
water channels
OR
antibiotic resistance
OR
other correct example

Determine the optimum concentration of sodium chloride for benzene degradation.

State the genus of halophilic bacteria in the soil that could be degrading the benzene.

1 mol dm^-3

Marinobacter

State two conditions in the fermenter that would be monitored by the probes.

Suggest a reason that the fermenter is surrounded by a water jacket.

Identify the waste gas produced.

Explain the process of penicillin production in the fermenter.

a. pH

b. temperature

c. oxygen levels

d. viscosity

e. foam

f. carbon dioxide

Accept any two conditions for the mark

[Max 1 Mark]

a. maintain constant temperature/insulation

b. cooling

[Max 1 Mark]

carbon dioxide/CO₂

a. inside of fermenter is sterilized «to prevent growth of other organisms»

b. «penicillin» fungus/Penicillium added to fermenter

c. nutrients are provided to allow the fungus to grow

d. when nutrients are used up, penicillin is produced

e. penicillin extracted from mixture in fermenter

f. penicillin purified ready for medical use

Accept named nutrient eg: glucose

[Max 3 Marks]

Identify the first triplets of each possible reading frame for this piece of DNA.

Define what is meant by an open reading frame.

AAT and ATG and TGC
OR
ATG and TGC and GCG ✔

All three triplets required.

a significant length of DNA that begins with a start codon and ends with a stop codon ✔

Significant length or similar phrase required

Identify the nucleotides of the start codon for the polypeptide.

State the chemical difference between the 5' end and the 3' end of a DNA strand.

Within the base sequence shown in the diagram, the sequence for the stop codon UGA appears. Explain the reasons for translation continuing beyond this point in the mRNA.

Describe how bioinformatics can help identify genes within the DNA of an organism.

AUG ✔

5′ end contains a phosphate group «on carbon 5»
OR
3′ carbon contains a hydroxyl/OH group «on carbon 3» ✔

a. the gene code occurs in triplets ✔

b. the stop codon would not be part of the reading frame ✔

c. the code for a polypeptide would contain more codons ✔

a. bioinformatics is the application of computer technology to biological information
OR
information is stored in a database
OR
bioinformatics is used in analyzing genomes ✔

b. allows for searches/comparisons/analysis of ORF/open reading frame ✔

c. the computer searches for a start codon and a stop codon «and within a distance of 60+ codons» ✔

Outline the emergent properties of biofilms.

Explain two ways in which bacteria of the genus Pseudomonas can be used for bioremediation.

a. the properties of the biofilm are greater than the sum of their individuals 

b. the properties are not predictable from looking at the individual

c. quorum sensing

d. adhere to a variety of substances

e. resistant to antibiotics / antimicrobial

f. formation of EPS

Cooperative aggregates on its own is not accepted. 

award [2 max]:

a. oil spills

b. oil is used as an organic source by the bacterium
OR
the bacterium changes the crude oil into less harmful substances

award [2 max]:

c. mercury from paint/fluorescent lights can leak into soil/water
OR
can form methyl mercury which travels along food chain/bioaccumulation

d. bacteria can remove methyl group from the methyl mercury/reduces toxicity

Allow other verified examples that include the danger to the environment (problem) and how the bacterium improves the situation (solution).

Describe the effect of the different sized particles on the treatment of these animal cells.

State one other physical method used to introduce DNA into plants.

a. there is little/no significant difference in the success of transfecting DNA 

b. there is «significantly» less damage to the cells with the smaller/40nm particles

electroporation / microinjection

Evaluate the effect of 1 % ginger root extract on biofilm formation.

Outline the importance of avoiding biofilm formation in pipes carrying drinking water.

a. bacteria spread out further with ginger/more than twice the distance with ginger/more spreading with ginger 

b. more spreading means less biofilm formation 

c. biofilms are usually made up of many species
OR
only tested the effect of ginger on one species 

d. only tested over 24 hours 

e. only tested with agar substrate/other substrates may have different effects

a. biofilms reduce flow rate in pipes 

b. contamination of the drinking water supplies by biofilm microbes 

c. biofilms may cause corrosion of pipes

Outline how the target gene is found using bioinformatics.

In this method of producing transgenic plants, state the name of the vector.

In this method of producing transgenic plants, state how to detect successful uptake of the gene.

In this method of producing transgenic plants, state one method used to introduce the vector into a plant.

Another method of plant transformation can be used to produce the hepatitis B vaccine. Outline the production of hepatitis B vaccine in tobacco plants.

a. open reading frame finder «ORF finder» detects sections of a DNA molecule likely to be genes
OR
search for significant length of DNA coding from a start codon to a stop codon ✔

b. BLASTn used to compare gene sequences coding for similar proteins in other organisms/databases ✔

c. BLASTp used to detect similar proteins in other organisms/databases ✔

Accept methionine/AUG as start codon and UAA/UAG/UGA as stop codon.

Accept any other verified software program.

plasmid / Ti ✔

a. antibiotic resistance ✔

b. presence of a marker gene ✔

c. B galactosidase ✔

Accept green fluorescent protein/GFP or other example of a marker gene.

a. infection by Agrobacterium tumefaciens

b. modification by calcium chloride / liposomes / electroporation / microinjection /gunshot / biolistics ✔

a. tobacco mosaic virus/TMV modified to carry gene of hepatitis B «surface antigen/HBsAg» ✔

b.«tobacco mosaic» virus infects tobacco plants 
OR 
its genetic material is incorporated into plant cells ✔

c. tobacco plants produce hepatitis B antigen ✔

d. «antigen» induces formation of antibodies/immune response «in humans» ✔

The question showed a diagram of the production of transgenic plants. Parts (a) and (c) proved difficult due to lack of specific vocabulary.

Part (b) was well answered.

Part (b) was well answered.

Part (b) was well answered.

Parts (a) and (c) proved difficult due to lack of specific vocabulary.

State the effect chlorination has on the accumulation of biofilm in the pipe.

Suggest why membrane filtration may be more suitable than chlorination in purifying the water.

Identify which two pipes would be required to study the effect of heat on biofilm accumulation.

Explain how quorum sensing benefits the bacteria within the steel pipes.

reduces «the accumulation of biofilm»

a. does not affect taste of water/no chemicals added

b. lower biofilm accumulation over time

[Max 1 Mark]

A and B

Both required

a. quorum sensing is a means of communication between bacteria

b. allows the bacteria to synchronize their activities/work together

c. they can change according to the environment/conditions in the pipe

d. control cell density/gene expression

[Max 2 Marks]

Suggest one material that could be loaded into the biogas fermenter from which biogas can be produced.

Identify the ideal temperature and oxygen conditions inside the fermenter for efficient biogas production.

Temperature:

Oxygen:

Distinguish between batch and continuous culture fermentation.

blackwater
OR
brownwater/sewage
OR
feces
OR
organic solid waste
OR
paper pulp
OR
other biodegradable material ✔

Do not accept methane and CO₂.

temperature warm and oxygen concentration low / anaerobic ✔ 

Accept above room temperature / 20 to 70°C for warm, depending on bacteria used.

Both required.

a. in batch culture product is withdrawn at the end of the «organisms» growth phases whereas in continuous culture product is withdrawn while the organism is growing / OWTTE ✔

b. in batch culture all of the growth medium/nutrients are added at the beginning whereas in continuous culture, growth medium/nutrients are added at a constant rate / OWTTE ✔

c. batch culture is carried out in large scale fermenters whereas continuous culture could be in small scale ✔

d. continuous can run for a longer time than batch ✔

State a suitable fungus for the production of citric acid in the fermenter.

Suggest a reason that fermentation is most successful at 30°C.

Suggest reasons for the changes in mass of sugar and citric acid after day 6.

State two uses of the citric acid produced.

Aspergillus/A niger/Aspergillus niger

enzymes work optimally/well/efficiently at this temperature

“Enzyme” is essential for the mark.

a. sugar consumption continues to increase because it is used in respiration / produces energy

b. products inhibit the reaction so no increase in citric acid
OR
negative feedback inhibits the reaction so no increase in citric acid
OR
decrease in pH may inhibit the enzymes

a. add a sour/acidic flavour to food/drink / change flavor / enhance taste

b. can act as a preservative in food/drink/cosmetics

c. controls pH in food/drink/cosmetics

Do not accept “food additive”.

State the role of microorganisms in bioremediation.

Explain the use of a named bacterium in bioremediation.

environmental pollution is removed by microorganisms

OWTTE

a. name of bacterium (genus required) and contaminating substance 

b. outline of one action of (this) bacterium to remove environmental contaminants from water or soil 

c. another detail of use of (this) bacterium to remove the contaminant 

d. advantage e.g. environmentally damaging chemicals not required / lower cost 

e. disadvantage e.g. may take longer / environmental conditions may not suit the bacterium

Full marks can only be given if a named example is given.

one example:
a. Pseudomonas (aeruginosa) to remove oil spills

b. uses crude oil for energy / breaks down crude oil

c. bacteria also need other chemicals/process may be speeded up by adding essential inorganic nutrients (phosphates/nitrates).

Suggest one undesirable consequence of cross-pollination involving glyphosate resistant crop plants with other plants.

Using the data, suggest one recommendation to farmers who plant transgenic soybeans.

Agrobacterium tumefaciens stains pink or red with the Gram stain. Deduce from this result what type of bacterium A. tumefaciens is.

Outline how A. tumefaciens is used to introduce genes into soybeans.

transfer of resistance genes to non-transgenic/organic crops
OR
transfer of resistance genes to wild relatives/development of weed resistance ✔

separate fields by at least 5m because at this distance no cross pollination occurs ✔

Needs a reason.

«Gram» negative ✔

a. genes to be transferred are introduced into a tumour-inducing/Ti plasmid/vector ✔

b. ‹embryo, seedling leaf› tissue is damaged/wounded / callus formed ✔

c. A. tumefaciens recognizes/is chemically attracted to damaged/wounded tissue ✔

d. A. tumefaciens transfers tumour-inducing/Ti plasmid/vector into plant cell ✔

e. plasmid integrates into plant cell genome ✔

Estimate the diameter of the zone of inhibition around the disc containing OPP in the S. aureus culture.

E. coli and P. aeruginosa are both Gram-negative bacteria and S. aureus is Gram-positive. Explain how it could be verified that S. aureus is a Gram-positive bacterium.

The three species of bacteria are commonly found on skin. Explain why excessive handwashing with HCP might lead to a P. aeruginosa infection.

P. aeruginosa is a concern in hospitals because it tends to form biofilms. Outline one reason for biofilms being particularly difficult to eradicate.

14–16 mm or 1.5–3 mm «around the disc» ✔

Units required

a. use the Gram staining procedure ✔

b. Gram-positive bacteria take up/retain «crystal violet» stain ✔ 

c. «Gram-positive bacteria» appear purple-coloured seen through a microscope ✔

a. P. aeruginosa not killed by the HCP
OR
disinfectant kills Gram-positive bacteria/S. aureus ✔ 

b. leading to less competition for P. aeruginosa ✔

microorganisms growing in a biofilm are resistant to antimicrobial agents ✔

The zone of inhibition was surprisingly poorly measured, even given the range and alternative measurements in the mark scheme. It is possible that when asked to estimate, candidates did not use a ruler.

Some answers referred back to the experiment, but where there was knowledge of Gram staining there were good answers.

It was often recognized that HCP was ineffective against P. aeruginosa but decreased competition was not seen.

Some correct answers were seen.

Suggest reasons for the use of a batch culture for the first fermentation and a continuous fermenter for the second fermentation.

Using the graph, explain the trend in biogas production over time in the fermenter without pre-treatment.

Suggest one reason for the higher methane content in biogas in pre-treated rice straw waste.

a. in batch culture the product is obtained just once
OR
the end products of digestion are required ✔

b. in the continuous fermenter biogas/methane is harvested constantly
OR
continuous fermentation is more productive, so ideal for production of methane ✔

a. first days the production is low as bacteria are few ✔

b. biogas production increases as time passes «from day 2 to day 12» as bacteria reproduce and increase «exponentially» ✔

c. biogas production levels off «between days 14 and 20» because bacterial population has reached optimum level ✔

d. biogas production decreases «from day 22 to day 30» because clogging/contamination / biofilm formation occurs
OR
no more reactants are added «between days 14 and 20» ✔

a. manure contains bacteria that digest cellulose to sugars ✔

b. more substrate/sugars to produce methane ✔

This question concerned the production of biogas from rice straw waste. The candidates had difficulty answering parts (a) and (c).

In part (b) most candidates simply described the graph with no explanation.

This question concerned the production of biogas from rice straw waste. The candidates had difficulty answering parts (a) and (c).

Compare and contrast the effect of ultrafiltration and nanofiltration on the drop in pressure.

State one other way in which the formation of biofilms can be inhibited.

Some biological systems show emergent properties. Emergent properties arise from the interaction of the component parts of a system that are not predictable from studying the individual components.

Explain how biofilms show emergent properties.

a. both cause pressure to drop ✔

b. pressure always higher in both compared to control ✔

c. nanofiltration causes least drop in pressure
OR
ultrafiltration causes the most drop in pressure ✔

d. the drop in pressure for ultrafiltration is more irregular than for nanofiltration ✔

using bacteriophages/viruses
OR
adding biocides/bactericides/chlorine
OR
using cell dispersal agents ✔

a. biofilms are composed of different species of bacteria/communities of microbes ✔

b. ‹biofilms› form an extracellular film/slime/EPS/exopolipeptide/exopolysaccharides ✔

c. microbes of biofilms show coordination/cooperation/quorum sensing ✔

d. individual microbes have a greater chance of survival in the biofilm «than on their own» ✔

e. biofilms have antibiotic resistance ✔

f. there are exchanges of nutrients between the microbes which is not possible for individual cells ✔

The picture shows workers cleaning up a polluted stretch of coastline in Alaska after oil was leaked from a tanker.

[Source: https://commons.wikimedia.org/wiki/File:OilCleanupAfterValdezSpill.jpg]

Explain how oil pollution can be treated by bioremediation.

a. bioremediation is the use of organisms to remove «or neutralize» pollutants

b. Pseudomonas species used in bioremediation of oil

c. oil biodegrades naturally at a very slow rate

d. bioremediation increases the rate that the oil breaks down

e. microorganisms feed/get energy from the oil

f. break the oil down into smaller nontoxic molecules

Accept other valid microorganism

[Max 4 Marks]

State the function of a marker gene.

Describe how genes are inserted into plants by electroporation.

Describe how an open reading frame (ORF) can be identified.

indicates successful uptake of recombinant DNA;

a. an electrical field/potential is applied to cells;

b. increases the permeability of the cell membrane (to DNA);

a. can be identified with bioinformatics software / example of software;

b. locate a sequence corresponding to a start codon/ATG (sense strand);

c. read this sequence until a stop codon/TGA/TAG /TAA is reached;

Outline how a gene gun inserts genes into plants.

Marker genes are often inserted together with the new gene. State the function of the marker genes.

Outline the characteristics of an open reading frame.

Explain, using an example, how gene transfer to a plant could help increase crop yield.

a. metal/tungsten/gold/bullet is coated with DNA/gene 

Biolistics on its own not accepted.

b. «this DNA is» fired in to a leaf containing the target cells

Accept any plant part, plant suspension, etc.

c. DNA is released and incorporated in to some of the cells

marker genes can be detected easily and show the gene has been inserted

Allow a specific example (eg, green fluorescent protein).

a. a length of DNA that codes for a polypeptide/protein
OR
length of DNA that can be translated

b. begins with start codon/TAC/ATG/DNA for methionine

c. stop codon occurs after sufficient length OWTTE.

a. name of GM plant eg: Soybean.

b. source of the inserted gene eg: (Cry1Ac gene) from Bacillus thuringiensis.
OR
organism used for transfer eg: plasmid from Agrobacterium tumefaciens.

c. purpose of the transfer eg: increased resistance to glyphosate herbicide.

d. how it increases yield eg: reduced competition with weeds killed by glyphosate.

Biogas production in a fermenter requires a substrate. State another requirement for this process.

Suggest reasons based on the data in the graph for increases in biogas production at Svensk Biogas.

Outline the principles of fermentation by continuous culture.

lack of oxygen/anoxic/anaerobic conditions / acidic pH / warm temperature / methanogens / acidogenic bacteria

a. increased variety of substrates used 

b. change in the proportion of substrates used
OR
from 1997 to 2004 increase in slaughterhouse waste 

c. less reliance on manure/increase use from food industry 

d. waste from food industry results in higher biogas yield

a. microbial population can be maintained in a state of exponential growth for a long time
OR
concentration of microorganisms in fermenter stable 

b. «balanced growth is» maintained by keeping nutrients/medium/pH/ temperature/ oxygen level constant 

c. nutrients are added AND products removed «at steady rate» 

d. probes used to monitor conditions within fermenters 

e. open fermentation/fermenter

State the year with the lowest EIQ for herbicides used in soybean growth in the US from 1998 to 2011.

Using the data from 1998 to 2004, evaluate whether the use of glyphosate has a greater impact on the environment than other herbicides.

Explain the role of Agrobacterium tumefaciens in introducing glyphosate resistance into soybean crops.

2006;

a. glyphosate use increased and other herbicide use decreased;

b. during this period there was no increase/decrease in the EIQ
OR
the data shows that there was not much change in environmental impact;

c. data insufficient to reach conclusion;

Both must be mentioned for the mark.

a. (Ti plasmid) modified to include a gene coding for glyphosate resistance;

b. the bacterium inserts a plasmid into plant cells;

c. the Ti plasmid induces tumours in plants;

d. (Ti plasmid) integrates its DNA into the plant genome
OR
plasmid is used as a vector to introduce glyphosate resistance gene;

e. tumour/gall tissue is cultured to form plants with the gene for glyphosate resistance;

The micrograph shows a T4 bacteriophage.

Discuss the use of bacteriophages in water systems.

a. bacteriophages are viruses of bacteria/prokaryotes ✔

b. each bacteriophage is specific to certain bacterial groups
OR
they can be used to target specific bacteria ✔

c. can be used in sewage plants
OR
can kill bacteria that cause water contamination/disinfect water
OR
can kill bacteria that form biofilms at water purification plants ✔

d. can kill strains resistant to antibiotics
OR
can kill strains resistant to chlorine/chemical disinfectants ✔

e. «presence of» bacteriophages also act as indicators of bacteria present ✔

f. generally not harmful to humans ✔

Trickle filter beds are used to treat sewage.

[Source: © International Baccalaureate Organization 2020.]

Explain the role of biofilms in sewage treatment.

a. biofilms are formed by bacteria;

b. bacteria in the biofilm secrete a matrix/EPS;

c. (matrix of biofilm) attaches (firmly) to the trickle bed/rocks/gravel/plastic/other media;

d. the biofilm breaks down organic material / feed on sewage
OR
the bacteria in the biofilm are saprophytic;

e. aerobic conditions are maintained through the bed / by aerating sprinklers;

Explain how plants can be genetically modified using the Ti plasmid so that they contain the gene for glyphosate resistance.

a. Ti plasmid is found in A tumefaciens / Agrobacterium 

b. add transgene along with antibiotic resistance gene into Ti plasmid 

c. Ti plasmid injected into host cell/plant «by A tumefaciens» 

d. Ti plasmid induces tumors 

e. Ti DNA becomes incorporated in host DNA 

f. apply antibiotic to select for cells that have been transformed

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

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

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. 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 ✔

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.

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.

Using this information, outline the reason for Golden rice being considered a transgenic organism.

Outline the bioinformatics method used to identify the target gene in the plant.

a. transgenic organisms produce proteins that were not previously part of their species’ proteome 

b. golden rice has genes belonging to other species «flower and bacterium» that were not there naturally/originally

database/NCBI/BLAST/BLASTn/BLASTp search «to find target gene» 

Outline a reason for inserting steam into the fermenter before fermentation.

Describe how optimal temperature is maintained inside the fermenter.

Explain how penicillin can be produced in a fermenter.

sterilizes/kills unwanted microorganisms in the fermenter;

cold water is added to the jacket if the temperature is too high;

a. takes place in (deep-tank) batch fermenters;

b. Penicillium (fungus) is grown on sugar/starch/nutrients;

c. penicillin is produced when the nutrients are used up;

d. penicillin secreted by the fungus is separated and purified;

e. occurs under aerobic conditions/Penicillium is an obligate aerobe;

Explain how microorganisms can be used in response to pollution incidents such as an oil spill.

a. «bioremediation» is the use of microbes to remove environmental contaminants from oil spill 

b. some pollutants are metabolized/degraded by microorganisms 

c. microorganisms can be eubacteria/archaeans  

d. microorganisms are useful in bioremediation because they can multiply very quickly «by binary fission» 

e. microorganisms can use pollutants/oil spills/crude oil as energy sources/carbon sources/electron acceptors in cellular respiration 

f. eg: Pseudomonas used «in bioremediation» 

g. Pseudomonas requires nutrients «such as potassium and urea» to metabolize the oil at a faster rate «so sprayed on to an oil spill to aid the bacteria in their work»

Transformed leaf discs containing recombinant DNA can be used to grow genetically modified crop plants. Discs taken from the new plant can be used to monitor successful uptake of the recombinant DNA.

State one other method by which recombinant DNA can be introduced into a plant.

Outline the role of bioinformatics in the genetic modification of plants.

Outline the potential advantages of genetically modified plants.

viral/bacterial vector / (micro)injection / electroporation / liposomes / biolistics

a. bioinformatics allows rapid analysis of large numbers of (genetic) samples 

b. target genes can be identified/recognized rapidly 

c. target gene linked to sequences that control its regulation are also identified 

d. target gene introduced into host

a. bulk production of important chemicals/medicines 

b. resistance to certain environmental conditions/pathogens 

c. resistance to herbicides/pesticides / pesticide production by plants (e.g. Bt corn) 

d. increase yield/nutritional value 

e. increase shelf life 

f. example of plant modified and nature / purpose of modification

Discuss the environmental risks of the cultivation of genetically modified crops.

a. antibiotic resistance «from marker genes» in the crops could be transferred to bacteria 

b. but this has never been demonstrated 

c. the precautionary principle should be applied 

d. genetically modified crops could hybridise with wild plants/other crops 

e. escape «of GM crop» could lead to outcompeting endemic species/wild plants / becoming invasive/superweed 

f. herbicide resistance could develop in wild plants
OR
pesticide resistance could develop in pests 

g. modifications can affect pollinating insects 

h. example of genetically modified crop 
eg Amflora potato / Bt maize

Explain the use of two named bacteria in response to pollution incidents.

a. bacteria metabolize pollutants
OR
bacteria used in bioremediation
OR
microorganisms use pollutant as an energy source/carbon source ✔

first named bacteria:
b. name of bacterium used in bioremediation «eg: Pseudomonas» ✔ Allow any other verified example.

c. name of pollutant/substrate «eg: oil/methyl mercury» ✔

d. product of degradation «eg: CO₂ and H₂O/elemental mercury» ✔

second named bacteria:
e. name of bacterium used in bioremediation «eg: Marinobacter» ✔ Allow any other verified example.

f. name of pollutant/substrate «eg: benzene» ✔

g. product of degradation «eg: CO₂» ✔

Award [3 max] if two bacteria are not named

Good explanations were given of the use of bacteria in response to pollution incidents. This was the best answered question in this option.

The diagram shows a biofilm that has formed on a tooth.

Using the diagram, explain the concept of emergent properties of biofilms.

a. «in biofilms» bacteria exhibit «emergent» properties not predictable from the individual components of the system
OR
biofilm exhibits its own properties, quite different in comparison with those shown by the single species 

b. biofilms form when bacteria adhere to surface of tooth and begin to excrete an EPS/extracellular polymeric substances/exopolysaccharides 

c. formation of EPS maintains bacteria together «in biofilm» 

d. interspecies relationships are favourable
OR
one species produces growth factors for/facilitates attachment of another species 

e. individual forces are low but the overall binding force can exceed that of covalent bonds 

f. glue properties/cohesiveness given by different types of bonding 

g. biofilms show resistance to antibiotics/other pathogen

Outline the process of quorum sensing in bacteria forming a biofilm.

Suggest one reason, other than quorum sensing, for the resistance to antibiotics of a biofilm.

a. cells/bacteria in a biofilm are close together ✔

b. cells secrete signaling molecules ✔

c. «signaling molecules» bind to receptors of other cells
OR
«signaling molecules» allow communication between cells ✔

d. a threshold is reached which enables emergent properties ✔

a. polysaccharide matrix/EPS does not let antibiotic pass/limits transport of antibiotic ✔

b. reduced metabolic activity/growth rate of bacteria in biofilm contributes to resistance ✔

c. increased cell density limits transport of antibiotic «to the interior of biofilm» ✔

d. «horizontal» transfer of antibiotic resistance via plasmids ✔

OWTTE

This question, about biofilm formation in a mammary gland, was poorly answered overall.

This question, about biofilm formation in a mammary gland, was poorly answered overall.

Explain the difficulties of treating microorganisms growing in biofilms.

a. biofilms show properties that are not shown by the individual cells / biofilms develop emergent
properties 

b. quorum sensing changes microbial behaviour / biofilms produce a matrix 

c. (matrix) hard to remove from a surface 

d. biofilms are tolerant to desiccation and heat shock 

e. biofilms may be very resistant to the action of (many) antibiotics/antimicrobial agents 

f. because cell division in biofilms is slow, antibiotics targeting this will be ineffective
OR
matrix forms a barrier to antibiotics