Biology • Year 12 • Module 6 • Lesson 17
Benefits of Genetic Technologies in Agricultural, Medical and Industrial Uses
Apply the three-domain framework to real industrial case studies: agricultural yield data on Bt cotton, scale-up of recombinant insulin manufacture, and engineered cellulase enzymes for second-generation biofuels.
1. Agricultural case — Bt cotton yield and insecticide use
Bt cotton has been engineered to express a Bacillus thuringiensis Cry-toxin gene, so the cotton plant produces an insecticidal protein toxic to bollworm caterpillars. The table below shows pooled means from on-farm trials (Australia and India, 2002–2018). 8 marks
| Metric (per hectare, mean) | Conventional cotton | Bt cotton | % change |
|---|---|---|---|
| Lint yield (kg) | 1620 | 2050 | +27% |
| Insecticide sprays per season | 9.1 | 2.4 | −74% |
| Insecticide active ingredient (kg) | 5.8 | 1.3 | −78% |
| Net farm income (AUD, indexed) | 100 | 138 | +38% |
| Bollworm-resistance reports (cumulative, by 2018) | — | Rising | — |
Source: pooled industry / regulatory trial summaries (after Qaim & Zilberman 2003; CSIRO Cotton CRC reports).
1.1 Describe two agricultural benefits of Bt cotton shown in the data, quoting at least one figure for each. 2 marks
1.2 Using lesson terminology, identify the type of agricultural benefit each figure represents (yield, resistance trait, nutritional modification, etc.) and link each to the relevant farmer outcome. 3 marks
1.3 The final row notes that bollworm-resistance reports are rising. Explain how this connects to the lesson's argument about biodiversity trade-offs and the limits of relying on a narrow range of genotypes. 3 marks
2. Medical case — recombinant insulin replaces animal-sourced insulin
Until 1982, all human insulin used to treat diabetes was extracted from pig and cow pancreases. After Genentech / Eli Lilly's recombinant human insulin (Humulin) was approved in 1982, production methods shifted to genetically engineered host cells (E. coli, later yeast). The graph below shows the global share of insulin produced by each method. 8 marks
Schematic based on Genentech/Eli Lilly approval (1982) and subsequent industry reporting; values illustrative.
2.1 Describe how the two curves change between 1978 and 2015. 2 marks
2.2 Genentech's recombinant insulin uses an inserted human insulin gene expressed inside E. coli (later baker's yeast). Explain three medical benefits of this production system over the older animal-pancreas method, using lesson language ("controlled biological systems", "useful protein production"). 3 marks
2.3 Insulin production is often listed as the textbook example of a medical benefit of genetic technologies. Briefly explain why an HSC evaluator would still want you to name a limitation (e.g. cost, access, infrastructure) rather than treat the case as purely positive. 3 marks
3. Industrial case — engineered cellulase enzymes in second-generation biofuels
Second-generation bioethanol uses plant residues (sugar-cane bagasse, straw) instead of food crops. The bottleneck is breaking the cellulose down into fermentable sugars. Companies including Novozymes and DSM produce cellulase enzymes from genetically engineered Trichoderma reesei fungi. The table below summarises typical industrial figures. 7 marks
| Process metric | Wild-type T. reesei (1990s) | Engineered T. reesei (post-2010) |
|---|---|---|
| Cellulase titre (g enzyme per L culture) | ~5 | ~100 |
| Enzyme cost per litre of bioethanol (USD) | ~1.00 | ~0.10 |
| Operating temperature (°C) | 30 | 50 |
| Cellulose conversion to glucose (%) | ~55 | ~90 |
Source: industry whitepapers (Novozymes Cellic CTec series, DSM Cellulosic Ethanol reports).
3.1 Quoting figures from the table, describe how genetic engineering of T. reesei has changed the cellulase production process. 2 marks
3.2 Identify two industrial benefits of genetic technologies illustrated by these data, using lesson terms ("industrial enzymes", "biological manufacturing", "consistency and scale"). 3 marks
3.3 Industrial cellulase enzymes are often described as greener than fossil-fuel processing. Briefly justify why this counts as an industrial benefit even though the technology operates inside engineered fungal cells, not on a farm. 2 marks
4. Cross-domain synthesis — write a domain-aware judgement
Using all three case studies above (Bt cotton, recombinant insulin, engineered cellulase), draft a single short paragraph (4–6 sentences) that would score in Band 5. Your paragraph must: 5 marks
- name at least one specific benefit per domain (agriculture, medicine, industry);
- name the agricultural biodiversity trade-off explicitly;
- finish with conditional, balanced language ("the technology can be highly beneficial, but…").
Q1.1 — Two agricultural benefits of Bt cotton (2 marks)
Any two of: increased yield (lint yield rose by 27%, from 1620 to 2050 kg/ha) [1]; reduced insecticide use (sprays per season fell by 74%, from 9.1 to 2.4; active-ingredient kg fell by 78%) [1]; higher net farm income (+38% indexed). Accept any two figures correctly cited.
Q1.2 — Type of agricultural benefit (3 marks)
Bt cotton illustrates a resistance trait (resistance to bollworm) that simultaneously delivers a productivity/yield benefit (less crop damage → more lint per hectare) [1]. Reduced spraying represents an input-efficiency benefit, lowering both farmer cost and environmental exposure to broad-spectrum insecticides [1]. Increased income shows the agronomic benefit also translates into an economic benefit for the grower [1]. (Nutritional modification is not shown by these data — accept this point if the student rules it out explicitly.)
Q1.3 — Rising bollworm resistance and biodiversity trade-off (3 marks)
Bt cotton works because virtually every plant in the field expresses the same Cry-toxin — a very narrow toxic profile [1]. Continuous exposure to one toxin selects strongly for rare bollworm individuals carrying resistance alleles, and over years their offspring come to dominate the pest population [1]. This is a clear example of the lesson's "narrow range of genotypes" warning: a single dominant genetic strategy (one toxin in one cultivar) produces short-term productivity gain but reduces long-term resilience as pest biodiversity selects around it. A strong response would also note that integrated refuge strategies (planting some non-Bt cotton) are designed to preserve diversity in the pest population and slow resistance [1].
Q2.1 — Trend description (2 marks)
Between 1978 and 1982 animal-extracted insulin supplied virtually 100% of the global market while recombinant insulin supplied 0% [1]. From the 1982 approval of Humulin onwards, the recombinant share rose rapidly and the animal-extracted share fell to near zero by 2010–2015, by which point recombinant insulin supplied roughly 95% or more of global insulin [1].
Q2.2 — Three medical benefits (3 marks)
(i) Useful protein production: the inserted human insulin gene means the recombinant product is structurally identical to human insulin, avoiding the small immunogenicity issues of pig/cow insulin [1]. (ii) Controlled biological systems: engineered E. coli or yeast in fermenters provide consistent, sterile, scalable production independent of livestock supply — meaning supply can be matched to global diabetic demand [1]. (iii) Treatment support / scale & consistency: each batch can be quality-controlled and dosing standardised, supporting safer long-term clinical use [1]. Accept also: avoids zoonotic contamination risk; not constrained by abattoir throughput.
Q2.3 — Why a limitation must still be named (3 marks)
Card 1 makes the point that a benefit is only meaningful "for something, to someone, compared with some alternative" — naming a limitation is what makes the evaluation defensible rather than promotional [1]. Real limitations include: recombinant insulin remains expensive in many low- and middle-income countries; access depends on intellectual property, cold-chain logistics and insurance/health-system support, not on the underlying biology [1]. Therefore even a textbook benefit must be qualified: "Recombinant insulin is a clear medical benefit of genetic technologies, but its real-world value depends on affordability and supply infrastructure" [1].
Q3.1 — Process description (2 marks)
Engineered T. reesei produces about 20× more cellulase per litre of culture (≈100 g/L vs ≈5 g/L) [1] and converts cellulose to glucose at ~90% efficiency vs ~55%, while enzyme cost per litre of bioethanol has fallen roughly tenfold (≈USD 0.10 vs ≈USD 1.00) [1].
Q3.2 — Two industrial benefits (3 marks)
(i) Industrial enzymes: genetic technologies allow production of cellulase at much higher titre and at higher operating temperature (50 °C), suiting it to large industrial fermenters [1]. (ii) Biological manufacturing at scale: lower per-litre enzyme cost and higher conversion efficiency make second-generation bioethanol commercially viable, turning plant residues into fuel [1]. (iii) Consistency and scale: engineered host strains produce predictable enzyme cocktails batch-to-batch, which the older wild-type process could not reliably deliver [1].
Q3.3 — Why "greener" still counts as an industrial benefit (2 marks)
"Industrial application" in this lesson covers any use of biological systems in manufacturing or processing [1]. Second-generation bioethanol replaces fossil-fuel inputs and uses crop residues that would otherwise be burned or discarded — the benefit operates at the manufacturing step, not the farm step, so it remains an industrial benefit even though it has downstream environmental effects [1].
Q4 — Cross-domain synthesis paragraph (5 marks)
Sample Band 5 paragraph. Genetic technologies deliver different kinds of benefit in different domains. In agriculture, Bt cotton expresses a Bacillus thuringiensis Cry-toxin gene and has increased lint yield by ~27% while cutting insecticide use by ~74%. In medicine, recombinant human insulin produced in engineered E. coli and yeast now supplies essentially the entire global insulin market, replacing animal-extracted insulin with a controlled biological production system. In industry, engineered Trichoderma reesei produces cellulase enzymes at ~20× higher titre, making second-generation bioethanol from plant residues economically viable. However, agricultural benefits cannot be evaluated in isolation: relying on a narrow range of cultivars (e.g. Bt cotton, Cavendish bananas, Roundup-Ready soy) narrows genetic diversity and selects for resistant pests, reducing resilience over time. The technology can therefore be highly beneficial across all three domains, but its benefits must be weighed against trade-offs, especially the biodiversity trade-off in agriculture.
Marking criteria. 1 mark each for: (a) named agricultural benefit with example; (b) named medical benefit with example; (c) named industrial benefit with example; (d) explicit biodiversity trade-off in agriculture; (e) conditional/balanced concluding sentence using lesson-style phrasing.