21. Biotechnology and genetic modification
- Syllabus
- 0610–2026–2027
- Section
- 21
- Level
- —
Exam analysis
Most tested topics
21.1 Biotechnology and genetic modification
- Syllabus
- 0610–2026–2027
- Topic
- 21.1
- Level
- —
Link bacterial features to biotechnology
Bacteria are useful in biotechnology and genetic modification because they reproduce rapidly and can make complex molecules.
| Feature | Why it is useful |
|---|---|
| rapid reproduction | a small starting culture quickly produces many bacterial cells, allowing fast large-scale production |
| ability to make complex molecules | bacteria can manufacture useful products rather than only simple raw materials |
The combined advantage is scale: rapid cell division creates many producers, and each cell can make the required complex molecule.
Rapid reproduction alone increases cell number; usefulness also depends on the cells producing the desired molecule.
Explain the ethical and plasmid advantages of bacteria
Bacteria offer two further advantages for biotechnology and genetic modification: few ethical concerns and the presence of plasmids.
| Advantage | Why it matters |
|---|---|
| few ethical concerns | manipulating and growing bacterial cultures generally raises fewer welfare concerns than manipulating animals |
| plasmids | these small circular DNA molecules can be removed, receive an inserted gene and be transferred back into a bacterium |
Once a useful gene is carried on a plasmid inside bacteria, the bacterial cells can copy the plasmid as they reproduce and use the gene to make its product.
A plasmid is a small circle of DNA, not the bacterium's main chromosome, nucleus or a mitochondrion.
21.2 Biotechnology
- Syllabus
- 0610–2026–2027
- Topic
- 21.2
- Level
- —
Use yeast respiration to produce ethanol fuel
Yeast respires anaerobically when oxygen is absent, converting glucose into ethanol and carbon dioxide while releasing some energy.
In biofuel production, yeast is supplied with sugars from plant material in oxygen-limited conditions. The ethanol produced is separated and used as a fuel.
Ethanol is the useful biofuel product; carbon dioxide is the other product. Oxygen must be limited so yeast carries out anaerobic rather than aerobic respiration.
Use yeast carbon dioxide to raise bread
In bread-making, yeast respires sugars anaerobically and releases carbon dioxide and ethanol.
Carbon dioxide forms bubbles that become trapped in the dough, causing it to expand and rise. During baking, heat kills the yeast and the ethanol evaporates, while the gas spaces remain in the bread.
Warm conditions speed yeast enzymes and respiration up to a suitable temperature; excessive heat denatures enzymes and kills the yeast.
Carbon dioxide—not ethanol—makes dough rise. Baking provides heat after the gas-producing stage; it does not supply the energy for yeast respiration.
Use pectinase to extract fruit juice
Pectinase breaks down pectin in fruit tissues during fruit-juice production.
Breaking pectin helps cells separate and releases more liquid, increasing the volume of juice that can be filtered. It also reduces suspended pectin, producing clearer juice.
Crushed fruit is mixed with pectinase under a suitable temperature and pH, then the juice is filtered from the remaining solids.
Pectinase acts on pectin; it is not lactase, protease or lipase. A water-only sample is a useful control when testing its effect.
Investigate enzyme washing powders fairly
Biological washing powders contain enzymes that digest stain molecules into smaller, more soluble products.
| Stain molecule | Enzyme | Products |
|---|---|---|
| starch | amylase | simple sugars |
| protein | protease | amino acids |
| fat | lipase | fatty acids and glycerol |
Compare equal stained fabric samples using equal volumes of water, equal powder amounts and the same washing time. Change only powder type or temperature, then measure stain removal using colour or percentage light reflected. Repeat and calculate a mean.
Biological powder can work well at moderate temperatures; above the enzymes' optimum, active sites change shape and activity falls through denaturation.
Match the enzyme to the stain substrate. A fair investigation changes one independent variable and controls the fabric, stain, time, water and powder amount.
Use lactase to make lactose-free milk
Lactase hydrolyses lactose in milk into glucose and galactose, producing milk suitable for people with lactose intolerance.
Milk can flow over lactase immobilised in alginate beads. Lactose molecules contact the enzyme and are broken down while the enzyme remains in the column.
Immobilised lactase can be reused, is easy to separate from the milk and does not contaminate the final product with enzyme.
Lactase breaks down lactose; it does not remove lactose by filtration and it is not lipase.
Use fermenters for large-scale products
Fermenters grow bacteria or fungi in large, controlled cultures so useful products can be made consistently at scale.
| Product | Production organism or role |
|---|---|
| insulin | genetically modified bacteria manufacture human insulin |
| penicillin | Penicillium fungus produces the antibiotic |
| mycoprotein | fungal biomass is grown as a protein-rich food product |
A sterile fermenter is inoculated with the chosen microorganism, supplied with nutrients and maintained under controlled conditions. The culture or product is harvested, separated and purified when required.
The useful output differs: insulin and penicillin are molecules recovered from the process, while mycoprotein is the fungal biomass itself.
Control five conditions inside a fermenter
Fermenter conditions are monitored and controlled to maximise microorganism growth or product yield without contamination or enzyme damage.
| Condition | Why and how it is controlled |
|---|---|
| temperature | respiration releases heat; a water jacket keeps the culture near the enzyme optimum and prevents denaturation |
| pH | metabolism can change acidity; probes and acid, alkali or buffers maintain an enzyme-suitable pH |
| oxygen | aerobic organisms need oxygen for respiration; sterile air is bubbled through and mixing distributes it |
| nutrient supply | carbon, nitrogen and mineral sources support respiration, growth and product formation; sterile feed is supplied at a suitable rate |
| waste products | wastes may become toxic or alter pH; gases leave through an outlet and culture products or liquid can be removed |
Stirrers keep temperature, pH, oxygen, nutrients and organisms evenly distributed and prevent cells from settling.
Sterility prevents competing microorganisms from using nutrients or contaminating the product. It is a process requirement, not a substitute for controlling the five named conditions.
21.3 Genetic modification
- Syllabus
- 0610–2026–2027
- Topic
- 21.3
- Level
- —
Define genetic modification
Genetic modification is changing the genetic material of an organism by removing, changing or inserting individual genes.
Because a gene is a section of DNA that codes for a product, altering an individual gene can give the organism a chosen characteristic or make it produce a chosen protein.
Genetic modification directly changes genes. Selective breeding instead chooses whole organisms as parents and does not directly remove, change or insert an individual gene.
Produce a human protein with genetically modified bacteria
A human gene can be transferred into a bacterial plasmid so bacteria express the gene and manufacture the human protein.
| Step | Required event |
|---|---|
| 1 | Isolate the DNA making up the human gene using a restriction enzyme; this forms sticky ends. |
| 2 | Cut a bacterial plasmid with the same restriction enzyme; this forms complementary sticky ends. |
| 3 | Insert the human gene into the plasmid and use DNA ligase to join the DNA, forming a recombinant plasmid. |
| 4 | Insert the recombinant plasmid into a bacterium; specific insertion details are not required. |
| 5 | Allow bacteria containing the recombinant plasmid to multiply. |
| 6 | The bacteria express the human gene and make the human protein. |
The same restriction enzyme is essential because it produces complementary sticky ends on the human gene and plasmid. Complementary bases can pair before DNA ligase seals the DNA backbone.
Restriction enzymes cut DNA; DNA ligase joins DNA. The inserted material is the human gene, not the finished protein, and the resulting DNA molecule is a recombinant plasmid.
Recognise four uses of genetic modification
Genetic modification transfers or alters genes to give an organism a specified useful outcome.
| Modified organism | Inserted gene gives… | Result |
|---|---|---|
| bacterium | instructions for a human protein | bacteria manufacture a human protein such as insulin |
| crop plant | herbicide resistance | the crop survives herbicide treatment used to control competing weeds |
| crop plant | resistance to insect pests | less pest damage and potentially less insecticide use |
| crop plant | improved nutritional quality | more of a useful nutrient, such as beta-carotene in rice |
The defining action is inserting a gene to create the stated trait. Applying herbicide or insecticide, using yeast in fermentation, and selecting resistant parents are not themselves examples of genetic modification.
Discuss benefits and risks of genetically modified crops
A sound discussion links each genetic change to a benefit and weighs it against economic, environmental, health or ethical risks. The balance may differ between crops such as soya, maize and rice.
| Possible advantage | Possible disadvantage or uncertainty |
|---|---|
| pest-resistant maize can suffer less insect damage, raise yield and require less insecticide, reducing cost and pollution | loss of an insect food source may disrupt food chains, and non-target insects or pollinators may be harmed |
| herbicide-resistant soya lets herbicide remove competing weeds while leaving the crop unharmed | resistance genes may spread by cross-pollination, or selection may favour herbicide-resistant weeds; fewer weeds can reduce biodiversity |
| nutritionally improved rice can provide an additional nutrient such as beta-carotene | the added amount may be insufficient, and unknown consumer health effects or objections may remain |
| resistance to disease, drought, salinity or cold can reduce losses and extend where crops grow | GM seed can cost more, may need repurchasing, and dependence on a narrow range of crops can reduce genetic diversity |
Benefits are not automatic: they depend on the inserted trait, local farming conditions and whether the promised yield, pesticide or nutritional outcome occurs. Risks can be reduced by measures such as preventing cross-pollination, but they still need monitoring.
Herbicide resistance protects the crop from herbicide; it does not make weeds disappear by itself. Separate evidence-based risks from unsupported claims that all GM food is either completely safe or necessarily harmful.