Ch 2 · 19.2 Genetic technology applied to medicine · AS & A Level Biology 9700
Topic 2 of 3 in Genetic technology — AS & A Level Biology 9700 — 39 lessons.
Introduction
Genetic technology already treats and prevents disease in three ways: GM microorganisms and cells make human proteins as medicines; genetic screening finds harmful alleles before symptoms appear; and gene therapy puts working copies of genes into patients' cells. Each raises social and ethical questions. (Syllabus section 19.2.)
Key ideas — Recombinant human proteins
The human gene for a protein is inserted into bacteria, yeast or cultured mammalian cells, which then make the human protein in large amounts.
🧑🏫 Teacher's explanation
Imagine you are a baker trying to make a very specific, high-quality sourdough bread. In the past, you had to rely on whatever wild yeast you could find in the local environment; sometimes it was great, sometimes it was inconsistent, and sometimes it was contaminated with mold. Recombinant technology is like taking the specific 'recipe' (the DNA sequence) for that perfect yeast and inserting it into a highly controlled, industrial-scale factory of standard baker's yeast. Now, every loaf is identical, safe, and produced in massive quantities.
📖 Definitions
🔍 Worked example — Easy
A patient requires insulin treatment for Type 1 diabetes. Compare the use of insulin extracted from bovine (cattle) pancreases versus recombinant human insulin in terms of immunological response.
🔍 Worked example — Standard
Explain why the use of recombinant Factor VIII is safer for a patient with haemophilia than using Factor VIII purified from human blood plasma.
🔍 Worked example — Exam-style
A researcher is using gene therapy to treat a patient with Severe Combined Immunodeficiency (SCID) caused by a lack of adenosine deaminase (ADA). Outline the process and state one advantage of this approach over traditional protein replacement.
⚠️ Common errors
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🎯 Exam question
(a) Explain how recombinant technology could be used to produce a replacement enzyme for this patient. [2] (b) Discuss the social and ethical considerations of using gene therapy to treat this condition. [3] [5 marks]
Key ideas — Genetic screening
Genetic screening tests people's DNA for alleles linked to a genetic disease, often before any symptoms appear.
Key ideas — Gene therapy
Gene therapy treats a genetic disease by inserting a functional allele into the patient's cells. The allele is carried by a vector, usually a harmless (disabled) virus, or a liposome. It is used for recessive conditions, where adding one working allele is enough.
🧑🏫 Teacher's explanation
Imagine a computer program that has a single line of broken code. This error causes the whole system to crash. Instead of trying to fix the broken line (which is incredibly difficult), you simply copy and paste a new, perfect version of that line into the system. The computer can now run correctly because the correct instructions are present, even though the original error remains in the background.
📖 Definitions
🔍 Worked example — Easy
A patient with SCID has a deficiency in the adenosine deaminase (ADA) enzyme. Explain why inserting a functional ADA gene into the patient's bone marrow stem cells can treat the disease.
🔍 Worked example — Standard
Compare the use of gene therapy in SCID versus Leber congenital amaurosis (an eye disease).
🔍 Worked example — Exam-style
A scientist is designing a gene therapy treatment. They must decide whether to target somatic cells or germ-line cells. Discuss the ethical implications of choosing germ-line therapy.
⚠️ Common errors
🧠 Quick check 1
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🎯 Exam question
(a) Explain why the use of a viral vector is necessary for this treatment. [2] (b) State one advantage of injecting the vector into the eye rather than into the bloodstream. [1] [3 marks]
Key ideas — Social and ethical considerations
🧑🏫 Teacher's explanation
Think of genetic technology like a high-tech repair shop for a computer. Recombinant proteins are like buying a pre-made, perfect replacement part instead of trying to fix a broken one. Gene therapy is like trying to rewrite a line of faulty code directly in the computer's hard drive.
📖 Definitions
🔍 Worked example — Easy
A patient undergoes genetic screening for the BRCA1 mutation. Explain why a positive result for the BRCA1 allele does not guarantee the patient will develop breast cancer.
🔍 Worked example — Standard
Compare the use of recombinant human insulin with traditional animal-derived insulin in the treatment of diabetes.
🔍 Worked example — Exam-style
A patient is undergoing gene therapy for SCID using a viral vector. Discuss two potential risks associated with this procedure.
⚠️ Common errors
🧠 Quick check 1
🧠 Quick check 2
🎯 Exam question
(a) State one potential biological risk of using a viral vector for this therapy. [1] (b) Discuss two ethical or social issues that arise from the widespread use of gene therapy. [3] [4 marks]
Worked example
Question. Factor VIII used to treat haemophilia was once purified from donated human blood. It is now produced by genetically modified mammalian cells. (a) Explain two advantages of using recombinant factor VIII. [2] (b) Explain why haemophilia could be a candidate for gene therapy. [2]
🔍 Worked example — Easy
A patient is being screened for the BRCA1 mutation. Explain why knowing the presence of this mutation is advantageous for the patient's clinical management.
🔍 Worked example — Standard
Compare the use of purified human blood-derived insulin versus recombinant human insulin in terms of production and safety.
🔍 Worked example — Exam-style
A patient has Severe Combined Immunodeficiency (SCID). Explain how gene therapy could potentially treat this condition.
⚠️ Common errors
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Practice
Answers