HSC Exam Practice

Sample response. Gene editing is the targeted alteration of a DNA sequence at a chosen location in the genome, typically using a tool such as CRISPR/Cas9 that combines a guide RNA with a nuclease to cut at a specific site.

Marking notes. 1 mark for "targeted alteration / change of DNA at a chosen / specific location"; 1 mark for naming or describing a specific mechanism (CRISPR, Cas9, guide RNA, nuclease).

Sample response. Synthetic biology — the design or redesign of biological systems for a specific purpose (e.g. engineered yeast strains for biological manufacturing of insulin or artemisinin precursors). Disease screening — the use of biotechnology to detect genetic risks or biological markers earlier and more accurately than older methods (e.g. non-invasive prenatal testing, expanded newborn screening panels). Precision breeding — using genetic knowledge or targeted tools to guide breeding outcomes more efficiently in agriculture (e.g. marker-assisted selection for disease-resistant wheat).

Marking notes. Award 1 mark per direction named correctly with a one-line aim, maximum 2 directions (2 marks) plus 1 mark for one being clearly distinguished from gene editing (i.e. not simply restating editing). Any two of synthetic biology, precision breeding, disease screening, targeted therapy accepted.

Sample response. An evidence-based prediction builds from demonstrated capability and uses cautious language ("may", "could", "has potential to"), and recognises that real-world benefit depends on safety, scalability, regulation and access. Hype assumes benefit is guaranteed because the technology is advanced, ignores feasibility and equitable access, and treats emerging directions as already universal solutions.

Marking notes. 1 mark for evidence-based prediction = grounded in current evidence + cautious language; 1 mark for hype = assumes benefit / ignores conditions; 1 mark for an explicit contrast on at least one of: language used, basis in evidence, treatment of feasibility / fairness.

Sample response. First, CRISPR can produce off-target edits when the guide RNA binds to partially complementary sequences elsewhere in the genome — this is a safety concern that requires extensive screening before any clinical use. Second, current approved CRISPR therapies (e.g. Casgevy for sickle cell disease) cost roughly US$2.2 million per patient, require specialised treatment centres and weeks of inpatient care, so they are not accessible to most patients with the conditions they treat. Third, only a small number of genetic conditions are currently addressable; for many inherited diseases the underlying biology, delivery, or somatic-vs-germline distinction is not yet solved.

Marking notes. Any two of: (i) off-target / safety issue; (ii) cost / access / infrastructure barrier; (iii) only a narrow set of conditions currently treatable; (iv) lack of long-term safety follow-up; (v) regulatory / ethical limits on germline editing. 1 mark per defensible reason (max 2). 1 mark for explicitly tying at least one reason to "guaranteed" — i.e. distinguishes potential from certainty.

Sample response. Need — what real problem does the technology address, and how important is that problem socially or biologically? Feasibility — can the technology work safely and reliably outside small trials, and can it be scaled and regulated? Fairness — who actually gets access to the benefit, and will deployment reduce or increase inequality?

Marking notes. 1 mark per criterion correctly named and explained. All three required for full marks.

Sample response (a). Published list prices range from approximately US$0.475 million (Kymriah) to US$3.5 million (Hemgenix), a roughly seven-fold range. The most expensive therapy shown is Hemgenix (haemophilia B); the least expensive is Kymriah (CAR-T for B-cell acute lymphoblastic leukaemia).

Sample response (b). US$3,500,000 ÷ US$80,000 per year = 43.75 years of median US household income. Approximately 43.8 years (or about 44 years to the nearest year).

Sample response (c). Although these therapies have met the lesson's feasibility criterion (FDA approval establishes safety and efficacy under regulated conditions), broad social benefit also requires fairness. At list prices ranging from US$0.475–3.5 million per patient — multiples of even the highest typical household incomes — direct payment is impossible for the vast majority of patients, and insurance / public health systems vary in willingness or capacity to reimburse. As a result, the population receiving the benefit is concentrated in well-insured patients in wealthy health systems, while the larger global population of patients with the underlying conditions does not yet access the technology. Feasibility is necessary but not sufficient for social benefit — fairness of access is the binding constraint.

Marking notes. Part (a) — 1 mark for stated range with both bounds; 1 mark for identifying both extremes by name. Part (b) — 1 mark for the correct division shown; 1 mark for the correct answer (43.75 or ~44 years). Part (c) — 1 mark for acknowledging that feasibility is met (FDA approval / efficacy); 1 mark for identifying cost as the immediate barrier; 1 mark for explicitly linking the barrier to fairness of access using the lesson's framework rather than just "it's expensive".

Sample response. Flaw 1 — "edits only the gene scientists want" misrepresents the precision of CRISPR: guide RNAs can bind partially complementary sequences elsewhere in the genome, producing off-target edits, which is exactly why approved therapies require extensive safety screening and long-term follow-up. Flaw 2 — "all inherited disease will be eliminated within ten years" treats the technology as a guaranteed universal solution and ignores feasibility (delivery, scalability, the limited number of conditions currently treatable, the somatic-vs-germline ethical line) and fairness (US$2.2 million list price for the one approved CRISPR therapy, treatment-centre availability, no current routes for most low- and middle-income settings). The article also implies the only remaining problem is regulatory speed, when in reality access, cost and equity are far larger constraints. A more defensible statement is: "CRISPR is a promising future direction in gene editing that may benefit patients with some inherited diseases — for example, Casgevy was approved in 2023 for sickle cell disease — but realising broad social benefit will depend on continued safety work to manage off-target effects, on cost reduction and infrastructure outside high-income settings, and on equitable access to approved therapies."

Marking notes. 1 mark for naming the off-target / precision flaw; 1 mark for naming a feasibility / scope flaw (e.g. "all inherited disease in ten years"); 1 mark for naming the fairness / access flaw (cost, infrastructure, distribution); 1 mark for a reformulation that uses cautious language ("may", "has potential to", "depends on"); 1 mark for the reformulation naming at least one specific real example (Casgevy, Luxturna, Zolgensma, CAR-T, etc.).

Sample response. The claim that emerging biotechnology will inevitably deliver major benefits overstates the case: in the framework used in this lesson, real social benefit depends on three conditions — need, feasibility and fairness — and a technology that meets one or two of these may still fail to deliver broad social benefit. Casgevy (exagamglogene autotemcel), an approved CRISPR-based gene therapy for sickle cell disease, demonstrates this clearly: the underlying need is real (sickle cell disease causes severe pain and reduced life expectancy and affects ~300,000 new births a year worldwide), and feasibility is established by FDA and MHRA approval. But fairness is limited by a list price of roughly US$2.2 million per patient and by the concentration of accredited treatment centres in a small number of wealthy health systems — so even an approved CRISPR therapy is currently a "future direction" rather than a "guaranteed benefit". By contrast, gene drives in Anopheles gambiae mosquitoes — designed using CRISPR to disrupt the doublesex female-fertility gene — remain experimental. Cage populations have collapsed to zero within 7–11 generations, which establishes technical feasibility, but the technology has not been authorised for field release anywhere in the world because of unresolved questions about recallability, cross-border spread, ecological knock-on effects and community consent. Both examples are real, currently relevant, and illustrate the lesson's central distinction: scientific possibility is not the same as broad social benefit. The defensible position is that emerging biotechnology has substantial potential to support agriculture, medicine and industry — earlier disease screening, more targeted therapies, more efficient breeding — but that benefit must be evaluated using need × feasibility × fairness, and described with cautious evidence-based language such as "may" and "has potential to". The claim of inevitability should therefore be rejected.

Marking notes. 1 mark — explicitly rejects "inevitable" / "guaranteed" framing and grounds rejection in the lesson's framework. 1 mark — names a currently approved emerging biotechnology with a real example (e.g. Casgevy, Luxturna, Zolgensma, CAR-T) and at least one specific feature. 1 mark — names an experimental emerging biotechnology with a real example (e.g. gene drives, somatic CRISPR in solid tumours, designer microbes, polygenic risk screening at population scale) and at least one specific feature. 1 mark — applies need with a problem statement. 1 mark — applies feasibility with a specific approval, safety or scalability point. 1 mark — applies fairness with a specific access, cost or governance point. 1 mark — closes with a justified evaluative judgement that uses cautious lesson language ("may", "has potential to", "if conditions are met") rather than absolute claims.