Free Gene Therapy OCR A Level Biology revision notes – covering specification point 6.1.3(h).
Gene therapy is the use of genetic engineering to treat genetic disorders by correcting, replacing, or modifying faulty genes.
Techniques used in gene therapy involve:
- Restoring gene function: Replacing or correcting a defective gene enables a functional or absent protein to be made (e.g. cystic fibrosis).
- Reducing or eliminating harmful gene activity: Disabling, suppressing, or silencing a faulty gene prevents the production of a harmful protein (e.g. Huntington’s disease).
- Giving cells a new therapeutic function: Adding a new gene gives a target cell a new function (e.g. T-cells recognising cancers).
Gene therapy can be categorised into two types, depending on the type of cell that is modified:
- Somatic cell gene therapy, which modifies the body cells of the patient, and is not inheritable.
- Germline* cell gene therapy, which modifies the gametes or a fertilised egg, and is inheritable.
*Germline therapy is predominantly written as ‘germ line’ in the official OCR A Level Biology textbook, and appears in this form as well as ‘germ-line’ in official exam questions and mark schemes. ‘Germline’ is the scientifically accepted form, but it will not matter for marking which way it is written.
Ethical Issues in Gene Therapy
The table below outlines some of the ethical issues associated with somatic cell gene therapy:
| Ethical issue | Explanation |
|---|---|
| High cost | Treatments are extremely expensive, so access may be limited to wealthier patients or healthcare systems. |
| Long-term effects | Many treatments are new, so long-term safety and efficacy may not be fully understood. |
| Therapeutic benefit | Can treat or reduce symptoms of genetic disorders, improving the quality of life. |
The table below outlines some of the ethical issues associated with germline cell gene therapy:
| Ethical issue | Explanation |
|---|---|
| Heritable genetic modification | Genetic modifications are inheritable:
|
| Lack of consent from future generations | Offspring of patients cannot give consent to the genetic modifications they will inherit. |
| Unequal access | Gene therapy is expensive, creating inequality between socioeconomic groups and countries. |