6.3.10Global Challenges

Gene Technology in Medicine — OCR Gateway GCSE Combined Science A J250 - Biology Revision Notes & Topical Questions

5 min read 9 parts Lesson 18 of 18

📚 OCR Gateway GCSE Combined Science A J250 - Biology Hub / Topical Revision

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Part 1 of 7Genetic engineering

Genetic engineering is the transfer of a gene from one organism into another, so that the recipient makes a new protein. The main steps:

Cut out

The gene for the required protein is identified and cut out of the donor DNA using restriction enzymes,

which cut at specific base sequences and may leave 'sticky ends'.

Vector

A vector, usually a bacterial plasmid (a small circle of DNA) or a virus, is cut open with the same enzyme.

DNA ligase

The gene is joined into the vector with DNA ligase, which seals the strands together.

The vector carries the gene into a host cell, such as a bacterium.

The host cells are grown in a fermenter, multiplying quickly and producing the protein in large amounts.

A famous example is human insulin for treating diabetes. The human insulin gene is put into bacteria, which then produce human insulin. This replaced insulin extracted from pigs and cattle, which could cause immune reactions. Other products include clotting factor for haemophilia and human growth hormone.

Part 2 of 7Gene therapy

Gene therapy aims to treat an inherited disorder by giving a patient a healthy copy of a faulty gene.

A virus modified to be harmless is often used as the vector to carry the working allele into the cells.

In cystic fibrosis, for example, the working allele could be delivered to the cells of the lungs; in some forms of inherited immune deficiency, treatment of the patient's own bone marrow cells has been successful.

Difficulties: getting the gene into enough cells, making the effect last, avoiding immune reactions and ensuring the gene is inserted in a safe place.

Changes to body cells are not passed on to the next generation,

whereas changes to gametes or embryos would be,
which is why germline editing is much more controversial.

Part 3 of 7Stem cells

Stem cells are undifferentiated cells that can divide and become specialised cells. Embryonic stem cells can become any type of cell. Adult stem cells, such as those in bone marrow, can form a more limited range of cells, for example blood cells.

Bone marrow transplants use these cells to replace blood cells in leukaemia patients.

Stem cells could in future be used to repair damaged tissues, for example in spinal injuries, diabetes and heart disease.

Therapeutic cloning

In therapeutic cloning an embryo with the same genes as the patient is made so that stem cells would not be rejected.

Plants also have stem cells in meristems, which can be used to clone crops.

Concerns include the destruction of embryos, which some people see as unacceptable, the risk of the cells growing out of control as tumours, and the possibility of viruses from donor cells.

Part 4 of 7Genetic testing and screening

People can be tested for alleles that cause or raise the risk of disease. Carrier testing lets couples know if they might have a child with a recessive disorder. Prenatal testing checks a foetus, and embryo screening (preimplantation genetic diagnosis) during IVF checks cells from an embryo before it is implanted. Newborn screening detects conditions that can be treated early. Adults may be offered tests for risk alleles, such as BRCA1, to allow preventative treatment.

Benefits	Concerns
Early treatment or prevention; informed decisions	Anxiety, particularly if no cure exists
Reduces the number of children born with serious disorders	Rejecting embryos is seen as wrong by some; possible 'designer babies'
Helps to choose the best drug	Insurance or employment discrimination; privacy of data

Part 5 of 7Evaluating gene technology

When evaluating a new technology in medicine, consider the benefit to patients, the cost and who can access it, risks and side effects, the effect on future generations, and ethical views.

Evaluating gene technology

For any question asking you to 'discuss', give arguments on both sides and make a reasoned conclusion.

Scientists can answer whether a technique works; whether it should be used is a decision for society, using ethical, social and economic arguments as well as scientific evidence.

Part 6 of 7Linking technologies: the example of diabetes

Diabetes shows how several technologies meet in one condition.

Genetic engineering gives a reliable supply of human insulin.

Stem cell research aims to replace the damaged insulin-producing cells.

Genetic testing can identify people at a higher risk of developing diabetes so that they can change their diet and lifestyle.

Each has its limits: insulin treats but does not cure; stem cell treatments are still experimental; and a test shows a risk, not a certainty.

Such comparisons help you to judge which technique is most useful in a specific situation.

Part 7 of 7Exam-style questions

Describe how bacteria can be genetically engineered to produce human insulin. [5]5 marks
Give one benefit and one concern of screening embryos for the cystic fibrosis allele. [2]2 marks
Explain why stem cells could be useful in treating diabetes. [2]2 marks

Key terms

Term	Meaning
Genetic engineering	Transferring a gene from one organism into another.
Restriction enzyme	An enzyme that cuts DNA at a specific base sequence.
DNA ligase	An enzyme that joins pieces of DNA together.
Plasmid	A small circle of DNA found in bacteria, used as a vector.
Gene therapy	Treating a disorder by introducing a healthy allele into cells.
Stem cell	An undifferentiated cell that can become specialised.
Embryo screening	Testing embryos for particular alleles before implantation.
Vector	A carrier used to insert a gene into a cell.

Avoid these mistakes

Saying that restriction enzymes join genes together; ligase joins, restriction enzymes cut.

Believing that gene therapy in body cells is passed to children.

Treating all stem cells as capable of becoming any cell type.

Writing that insulin from bacteria is bacterial insulin; it is human insulin.

Giving ethical views as facts, instead of presenting them as arguments.

Last updated: 20 October 2026