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19.2 Genetic Technology Applied to Medicine

Syllabus
9700–2028–2029
Topic
19.2
Level
A2

Recombinant human proteins replace missing functions

Genetically modified microbes or cultured cells can make human proteins in large, controlled batches. The purified recombinant protein replaces or supplements a protein whose absence or deficiency causes disease.

Recombinant protein Treatment role Particular advantage
Insulin helps people with diabetes control blood glucose concentration human sequence is less likely than animal insulin to cause an immune/allergic response and avoids animal-source objections
Factor VIII restores part of the clotting pathway in haemophilia A avoids dependence on donated blood and greatly reduces transfer of blood-borne pathogens
Adenosine deaminase (ADA) supplies enzyme activity missing in some people with SCID, supporting lymphocyte/immune function provides a defined human enzyme when the patient's own functional ADA is insufficient

Shared advantages include a reliable large-scale supply, consistent composition, easier standardisation and purification, reduced dependence on animals or human donors, lower infection risk, and fewer religious or ethical objections to the source. Production can be adjusted to match demand.

Recombinant production reduces source-related problems but does not make treatment risk-free. Purity, correct folding, dose, route, immune reactions and manufacturing quality still require control; replacement protein may also need repeated administration.

Genetic screening turns inherited information into earlier choices

Genetic screening tests people or populations for alleles associated with inherited disease. Its advantage is earlier, more specific information that can guide monitoring, treatment, counselling and reproductive decisions before symptoms or an affected birth.

Example What a positive result indicates Advantages of knowing
BRCA1/BRCA2 variants increased risk of breast and some other cancers, not certainty of cancer more frequent surveillance, earlier detection/treatment, risk-reducing choices, testing of relatives and informed family planning
Huntington's disease allele a predictive result for a usually late-onset dominant disorder future care, work and financial planning; counselling; reproductive choices; a negative result may end uncertainty
Cystic fibrosis alleles two disease alleles can support diagnosis; one allele identifies a carrier carrier screening of couples, prenatal/newborn information, earlier treatment and respiratory/nutritional management, informed reproductive choices

A targeted programme can be cost-effective when it screens for well-characterised variants common in the population. Earlier identification can reduce complications or mortality when surveillance or treatment is available, and results can inform biologically related family members.

Interpret the result according to the condition: BRCA variants alter risk, Huntington's testing is predictive, and cystic-fibrosis testing may show affected or carrier status. Screening accuracy and variant interpretation still require confirmation and genetic counselling.

Gene therapy delivers a functional allele to affected cells

Gene therapy treats a genetic disease by delivering a functional allele, or making a corrective DNA change, in the somatic cells where the missing protein is needed. Expression of the functional gene restores some of the lost cell function.

  1. Identify the faulty gene and target tissue.
  2. Place a functional allele in a suitable vector, often a modified virus.
  3. Deliver the vector directly to the tissue or modify the patient's cells outside the body and return them.
  4. The target cells take up the gene and transcribe/translate it.
  5. Functional protein improves the affected pathway; monitor expression, benefit and adverse effects.
Disease example Target and route Intended result
ADA-deficiency SCID remove patient lymphocytes or blood-forming stem cells, introduce a functional ADA allele with a vector, then return modified cells ADA is produced, toxic metabolites are reduced and immune-cell function improves; short-lived lymphocytes may require repeat treatment, while modified stem cells may last longer
Inherited eye disease such as LCA2 inject a vector carrying a functional allele such as RPE65 into/near retinal target cells retinal cells express the functional protein and may preserve or improve vision; the eye is small, accessible and relatively isolated from systemic immune responses

Somatic gene therapy changes treated cells, not every cell and usually not the gametes, so the change is not inherited. Success depends on reaching enough suitable cells, expression lasting long enough, and avoiding immune reactions or harmful insertion/editing effects.

Genetic medicine balances benefit, autonomy, risk and access

A social and ethical discussion asks who benefits, who bears risk, who decides and whether access is fair. Genetic screening produces information affecting individuals and relatives; gene therapy actively changes cells and may involve uncertain long-term effects.

Consideration Potential benefit Concern or cost
Screening and timing early diagnosis can allow monitoring or treatment before irreversible symptoms false results or uncertain variants can cause unnecessary treatment, reassurance or anxiety
Consent and family informed people can plan care and reproduction; relatives may also learn relevant risk newborns or future children cannot fully consent; one person's result reveals information about relatives who may not want to know
Privacy and discrimination shared records can coordinate care and research insurers, employers or others could misuse genetic information if confidentiality is weak
Gene-therapy safety one treatment may restore function or prevent severe disability immune responses, harmful insertion/editing and unknown long-term effects may affect the patient
Cost and access effective screening can target scarce treatment early expensive programmes and therapies may widen inequality or divert resources from other care

A defensible decision states the context and weighs evidence. For example, newborn screening is stronger when disease is serious, the test is accurate and early treatment changes the outcome; its case weakens if follow-up treatment is unavailable or unaffordable. Counselling, voluntary informed consent where possible, data protection and long-term monitoring reduce—but do not remove—the concerns.

Somatic therapy affects the treated person; germline changes could pass to future generations who cannot consent and therefore raise an additional ethical boundary. Do not present 'ethical' as one fixed answer: identify stakeholders, benefit, evidence, uncertainty and a reasoned conclusion.