Explain gene therapy examples
Outline gene therapy for SCID and inherited eye disease and qualify its limits.
A Level; Cambridge International Biology 9700, 2028–2030. This is curriculum teaching, not medical advice or a claim that a treatment is suitable for an individual. Written responses are self-checked
Before you begin
- DNA stores genetic information; genes can be expressed to produce RNA and protein.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the basic aim of gene therapy in a genetic disease?
What you will learn
- Describe delivery of a functional gene to relevant cells
- Use SCID and inherited eye disease as examples
Build the explanation
Gene therapy aims to treat a genetic disease by delivering a functional gene sequence to relevant cells so they can make a needed product. In some forms of severe combined immunodeficiency (SCID), gene therapy targets blood-forming cells; inherited eye-disease treatment can deliver a functional gene to cells in the retina. The approach depends on the gene, target tissue and delivery method.
Use the evidence carefully
Delivery, immune response, durability and control of expression affect outcome. Somatic gene therapy changes treated cells, not necessarily eggs or sperm; it is distinct from germline editing. Suitability and risk are clinical questions, not determined by the syllabus example alone.
Pause and explain
Name two factors that can limit gene-therapy success after delivery.
Worked example
A functional gene is delivered to retinal cells affected by an inherited disorder. What approach is illustrated?
Show the worked solution
- The target tissue is the retina.
- The goal is restored or improved function.
Answer Gene therapy for an inherited eye disease.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Why must a gene-therapy vector reach the relevant tissue?
Give me a hint
Identify the relevant material or technology and explain each step.
Compare my reasoning
- The target cells need the functional sequence.
- Unreached cells will not be corrected by that treatment.
The functional gene must reach the cells where its product is needed, such as relevant blood-forming cells or retinal cells.
Look for these in your work
- Method identified
- Steps linked to function
A treated patient’s egg cells are not changed. What does this imply about the therapy?
Give me a hint
Use the stated example to justify a conclusion.
Compare my reasoning
- The change is somatic.
- It is not necessarily inherited by offspring.
It is somatic gene therapy affecting treated body cells; it is not necessarily passed to offspring.
Look for these in your work
- Evidence interpreted
- Limits stated
Name two factors that can limit gene-therapy success after delivery.
Give me a hint
Apply the idea to a new application or trade-off.
Compare my reasoning
- Expression or persistence may vary.
- Immune response or target-cell access may matter.
Success can be limited by target-cell delivery, immune responses, duration of expression, gene regulation or unintended effects.
Look for these in your work
- Application explained
- Claim appropriately bounded
Common mistakes
- Saying gene therapy always cures a disorder
- Confusing somatic therapy with inherited germline change
What can you explain now?
What is the basic aim of gene therapy in a genetic disease?
Compare with the explanation
Deliver a functional gene to relevant cells
The target cells may then express the needed product.
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Make it stick
How does gene therapy differ from genetic screening?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.